diff --git a/src/avra.c b/src/avra.c
index 5aec61d..8c2fbc3 100644
--- a/src/avra.c
+++ b/src/avra.c
@@ -28,6 +28,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <inttypes.h>
 #include <string.h>
 
 #include "misc.h"
@@ -259,7 +260,7 @@ assemble(struct prog_info *pi)
 int
 load_arg_defines(struct prog_info *pi)
 {
-	int i;
+	int64_t i;
 	char *expr;
 	char buff[256];
 	struct data_list *define;
@@ -285,13 +286,13 @@ load_arg_defines(struct prog_info *pi)
 			if (def_const(pi, buff, i)==False)
 				return (False);
 		} else { /* Pass 2 */
-			int j;
+			int64_t j;
 			if (get_constant(pi, buff, &j)==False) {  /* Defined in Pass 1 and now missing ? */
 				fprintf(stderr,"Constant %s is missing in pass 2\n",buff);
 				return (False);
 			}
 			if (i != j) {
-				fprintf(stderr,"Constant %s changed value from %d in pass1 to %d in pass 2\n",buff,j,i);
+				fprintf(stderr,"Constant %s changed value from %" PRId64 " in pass1 to %" PRId64 " in pass 2\n",buff,j,i);
 				return (False);
 			}
 			/* OK. Definition is unchanged */
@@ -458,7 +459,7 @@ print_msg(struct prog_info *pi, int type, char *fmt, ...)
 
 
 int
-def_const(struct prog_info *pi, const char *name, int value)
+def_const(struct prog_info *pi, const char *name, int64_t value)
 {
 	struct label *label;
 	label = malloc(sizeof(struct label));
@@ -651,7 +652,7 @@ test_orglist(struct segment_info *si)
 
 /* Get the value of a label. Return FALSE if label was not found */
 int
-get_label(struct prog_info *pi,char *name,int *value)
+get_label(struct prog_info *pi,char *name,int64_t *value)
 {
 	struct label *label=search_symbol(pi,pi->first_label,name,NULL);
 	if (label==NULL) return False;
@@ -660,7 +661,7 @@ get_label(struct prog_info *pi,char *name,int *value)
 }
 
 int
-get_constant(struct prog_info *pi,char *name,int *value)
+get_constant(struct prog_info *pi,char *name,int64_t *value)
 {
 	struct label *label=search_symbol(pi,pi->first_constant,name,NULL);
 	if (label==NULL) return False;
@@ -669,7 +670,7 @@ get_constant(struct prog_info *pi,char *name,int *value)
 }
 
 int
-get_variable(struct prog_info *pi,char *name,int *value)
+get_variable(struct prog_info *pi,char *name,int64_t *value)
 {
 	struct label *label=search_symbol(pi,pi->first_variable,name,NULL);
 	if (label==NULL) return False;
diff --git a/src/avra.h b/src/avra.h
index 363d91f..8b96a61 100644
--- a/src/avra.h
+++ b/src/avra.h
@@ -30,6 +30,7 @@
 
 #include <stdio.h>
 #include <time.h>
+#include <stdint.h>
 
 #define IS_HOR_SPACE(x)	((x == ' ') || (x == 9))
 #define IS_LABEL(x)	(isalnum(x) || (x == '%') || (x == '_'))
@@ -221,7 +222,7 @@ struct def {
 struct label {
 	struct label *next;
 	char *name;
-	int value;
+	int64_t value;
 };
 
 struct macro {
@@ -286,7 +287,7 @@ void init_segment_size(struct prog_info *pi, struct device *device);
 void rewind_segments(struct prog_info *pi);
 void advance_ip(struct segment_info *si, int offset);
 
-int def_const(struct prog_info *pi, const char *name, int value);
+int def_const(struct prog_info *pi, const char *name, int64_t value);
 int def_var(struct prog_info *pi, char *name, int value);
 int def_orglist(struct segment_info *si);
 int fix_orglist(struct segment_info *si);
@@ -294,9 +295,9 @@ void fprint_orglist(FILE *file, struct segment_info *si, struct orglist *orglist
 void fprint_sef_orglist(FILE *file, struct segment_info *si);
 void fprint_segments(FILE *file, struct prog_info *pi);
 int test_orglist(struct segment_info *si);
-int get_label(struct prog_info *pi,char *name,int *value);
-int get_constant(struct prog_info *pi,char *name,int *value);
-int get_variable(struct prog_info *pi,char *name,int *value);
+int get_label(struct prog_info *pi,char *name,int64_t *value);
+int get_constant(struct prog_info *pi,char *name,int64_t *value);
+int get_variable(struct prog_info *pi,char *name,int64_t *value);
 struct label *test_label(struct prog_info *pi,char *name,char *message);
 struct label *test_constant(struct prog_info *pi,char *name,char *message);
 struct label *test_variable(struct prog_info *pi,char *name,char *message);
@@ -321,15 +322,15 @@ char *get_next_token(char *scratch, int term);
 char *fgets_new(struct prog_info *pi, char *s, int size, FILE *stream);
 
 /* expr.c */
-int get_expr(struct prog_info *pi, char *data, int *value);
-int get_symbol(struct prog_info *pi, char *label_name, int *data);
+int get_expr(struct prog_info *pi, char *data, int64_t *value);
+int get_symbol(struct prog_info *pi, char *label_name, int64_t *data);
 int par_length(char *data);
 
 /* mnemonic.c */
 int parse_mnemonic(struct prog_info *pi);
 int get_mnemonic_type(struct prog_info *pi);
 int get_register(struct prog_info *pi, char *data);
-int get_bitnum(struct prog_info *pi, char *data, int *ret);
+int get_bitnum(struct prog_info *pi, char *data, int64_t *ret);
 int get_indirect(struct prog_info *pi, char *operand);
 int is_supported(struct prog_info *pi, char *name);
 int count_supported_instructions(int flags);
diff --git a/src/coff.c b/src/coff.c
index 657592a..7ed94e0 100644
--- a/src/coff.c
+++ b/src/coff.c
@@ -706,7 +706,7 @@ int
 stab_add_lineno(struct prog_info *pi, int LineNumber, char *pLabel, char *pFunction)
 {
 
-	int Address;
+	int64_t Address;
 	struct lineno *pln;
 	struct syment *pEntry;
 	union auxent *pAux;
@@ -754,7 +754,7 @@ int
 stab_add_lbracket(struct prog_info *pi, int Level, char *pLabel, char *pFunction)
 {
 
-	int Address;
+	int64_t Address;
 	struct syment *pEntry;
 	union auxent *pAux;
 
@@ -790,7 +790,7 @@ int
 stab_add_rbracket(struct prog_info *pi, int Level, char *pLabel, char *pFunction)
 {
 
-	int Address;
+	int64_t Address;
 	struct syment *pEntry;
 	union auxent *pAux;
 
@@ -907,7 +907,8 @@ int
 stab_add_function(struct prog_info *pi, char *pName, char *pLabel)
 {
 
-	int n, Address;
+	int n;
+	int64_t Address;
 	unsigned short CoffType, Type;
 	struct syment *pEntry;
 	char *pType;
@@ -991,7 +992,8 @@ int
 stab_add_global(struct prog_info *pi, char *pName, char *pType)
 {
 
-	int n, Address, IsArray, SymbolIndex;
+	int n, IsArray, SymbolIndex;
+	int64_t Address;
 	unsigned short CoffType, Type;
 	struct syment *pEntry;
 	char *p;
@@ -1129,7 +1131,8 @@ int
 stab_add_static_symbol(struct prog_info *pi, char *pName, char *pType, char *pLabel)
 {
 
-	int n, Address;
+	int n;
+	int64_t Address;
 	unsigned short CoffType, Type;
 	struct syment *pEntry;
 
diff --git a/src/coff.h b/src/coff.h
index 5db2fa4..efc4e56 100644
--- a/src/coff.h
+++ b/src/coff.h
@@ -123,8 +123,8 @@ struct external_scnhdr {
 
 struct lineno {
 	union {
-		long  l_symndx;  /* symtbl index of func name */
-		long  l_paddr;   /* paddr of line number */
+		int64_t  l_symndx;  /* symtbl index of func name */
+		int64_t  l_paddr;   /* paddr of line number */
 	} l_addr;
 	unsigned short  l_lnno;    /* line number */
 };
diff --git a/src/device.c b/src/device.c
index 286d64f..98844cb 100644
--- a/src/device.c
+++ b/src/device.c
@@ -27,6 +27,7 @@
 
 
 #include <stdlib.h>
+#include <inttypes.h>
 #include <string.h>
 
 #include "misc.h"
@@ -189,7 +190,7 @@ struct device *get_device(struct prog_info *pi, char *name)
 int
 predef_dev(struct prog_info *pi)
 {
-	int i;
+	int64_t i;
 	char temp[MAX_DEV_NAME+1];
 	def_dev(pi);
 	for (i=0; (!i)||(device_list[i].name); i++) {
@@ -206,13 +207,13 @@ predef_dev(struct prog_info *pi)
 			if (def_const(pi, temp, i)==False)
 				return (False);
 		} else { /* Pass 2 */
-			int j;
+			int64_t j;
 			if (get_constant(pi, temp, &j)==False) {  /* Defined in Pass 1 and now missing ? */
 				fprintf(stderr,"Constant %s is missing in pass 2\n",temp);
 				return (False);
 			}
 			if (i != j) {
-				fprintf(stderr,"Constant %s changed value from %d in pass1 to %d in pass 2\n",temp,j,i);
+				fprintf(stderr,"Constant %s changed value from %"PRId64" in pass1 to %"PRId64" in pass 2\n",temp,j,i);
 				return (False);
 			}
 			/* OK. definition is unchanged */
diff --git a/src/directiv.c b/src/directiv.c
index 5627516..1ee4cd6 100644
--- a/src/directiv.c
+++ b/src/directiv.c
@@ -28,6 +28,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <inttypes.h>
 #include <ctype.h>
 
 #include "misc.h"
@@ -157,7 +158,7 @@ parse_directive(struct prog_info *pi)
 {
 	int directive, pragma;
 	int ok = True;
-	int i;
+	int64_t i;
 	char *next, *data, buf[140];
 	struct file_info *fi_bak;
 
@@ -329,7 +330,7 @@ parse_directive(struct prog_info *pi)
 				if (pi->list_line && pi->list_on) {
 					fprintf(pi->list_file, "          %s\n", pi->list_line);
 					pi->list_line = NULL;
-					fprintf(pi->list_file, "%c:%06lx %04x\n",
+					fprintf(pi->list_file, "%c:%06lx %04"PRIx64"\n",
 					        pi->segment->ident, pi->segment->addr, i);
 				}
 				if (pi->segment == pi->eseg) {
@@ -375,13 +376,13 @@ parse_directive(struct prog_info *pi)
 			if (def_const(pi, next, i)==False)
 				return (False);
 		} else { /* Pass 2 */
-			int j;
+			int64_t j;
 			if (get_constant(pi, next, &j)==False) {  /* Defined in Pass 1 and now missing ? */
 				print_msg(pi, MSGTYPE_ERROR, "Constant %s is missing in pass 2", next);
 				return (False);
 			}
 			if (i != j) {
-				print_msg(pi, MSGTYPE_ERROR, "Constant %s changed value from %d in pass1 to %d in pass 2", next,j,i);
+				print_msg(pi, MSGTYPE_ERROR, "Constant %s changed value from %"PRId64" in pass1 to %"PRId64" in pass 2", next,j,i);
 				return (False);
 			}
 			/* OK. Definition is unchanged */
@@ -556,13 +557,13 @@ parse_directive(struct prog_info *pi)
 			if (def_const(pi, next, i)==False)
 				return (False);
 		} else { /* Pass 2 */
-			int j;
+			int64_t j;
 			if (get_constant(pi, next, &j)==False) {  /* Defined in Pass 1 and now missing ? */
 				print_msg(pi, MSGTYPE_ERROR, "Constant %s is missing in pass 2", next);
 				return (False);
 			}
 			if (i != j) {
-				print_msg(pi, MSGTYPE_ERROR, "Constant %s changed value from %d in pass1 to %d in pass 2", next,j,i);
+				print_msg(pi, MSGTYPE_ERROR, "Constant %s changed value from %"PRId64" in pass1 to %"PRId64" in pass 2", next,j,i);
 				return (False);
 			}
 			/* OK. Definition is unchanged */
@@ -796,7 +797,7 @@ term_string(struct prog_info *pi, char *string)
 int
 parse_db(struct prog_info *pi, char *next)
 {
-	int i;
+	int64_t i;
 	int count;
 	char *data;
 	char prev = 0;
@@ -831,8 +832,8 @@ parse_db(struct prog_info *pi, char *next)
 				if (!get_expr(pi, next, &i))
 					return (False);
 				if ((i < -128) || (i > 255))
-					print_msg(pi, MSGTYPE_WARNING, "Value %d is out of range (-128 <= k <= 255). Will be masked", i);
-				if (pi->list_on) fprintf(pi->list_file, "%02X", i);
+					print_msg(pi, MSGTYPE_WARNING, "Value %"PRId64" is out of range (-128 <= k <= 255). Will be masked", i);
+				if (pi->list_on) fprintf(pi->list_file, "%02"PRIX64, i);
 			}
 			count++;
 			write_db(pi, (char)i, &prev, count);
@@ -920,7 +921,7 @@ spool_conditional(struct prog_info *pi, int only_endif)
 int
 check_conditional(struct prog_info *pi, char *pbuff, int *current_depth, int *do_next, int only_endif)
 {
-	int i = 0;
+	int64_t i = 0;
 	char *next;
 	char linebuff[LINEBUFFER_LENGTH];
 
diff --git a/src/expr.c b/src/expr.c
index 8d8baea..79e57e0 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -27,6 +27,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 #include <ctype.h>
 
@@ -77,7 +78,7 @@ enum {
 
 struct element {
 	struct element *next;
-	int data;
+	int64_t data;
 };
 
 char *function_list[] = {
@@ -96,16 +97,16 @@ char *function_list[] = {
 	"log2"
 };
 
-int
-log_2(int value)
+int64_t
+log_2(int64_t value)
 {
-	int i = 0;
+	int64_t i = 0;
 	while (value >>= 1)
 		i++;
 	return (i);
 }
 
-int
+int64_t
 get_operator(char *op)
 {
 	switch (op[0]) {
@@ -197,8 +198,8 @@ test_operator_at_precedence(int operator, int precedence)
 }
 
 
-int
-calc(struct prog_info *pi, int left, int operator, int right) /* TODO: Sjekk litt resultater */
+int64_t
+calc(struct prog_info *pi, int64_t left, int64_t operator, int64_t right) /* TODO: Sjekk litt resultater */
 {
 	switch (operator) {
 	case OPERATOR_MUL:
@@ -250,7 +251,7 @@ calc(struct prog_info *pi, int left, int operator, int right) /* TODO: Sjekk lit
 }
 
 /* If found, return the ID of the internal function */
-int
+int64_t
 get_function(char *function)
 {
 	int i;
@@ -271,8 +272,8 @@ get_function(char *function)
 	return (-1);
 }
 
-unsigned int
-do_function(int function, int value)
+uint64_t
+do_function(int function, int64_t value)
 {
 	switch (function) {
 	case FUNCTION_LOW:
@@ -302,7 +303,7 @@ do_function(int function, int value)
 
 
 int
-get_symbol(struct prog_info *pi, char *label_name, int *data)
+get_symbol(struct prog_info *pi, char *label_name, int64_t *data)
 {
 	struct label *label;
 	struct macro_call *macro_call;
@@ -343,7 +344,7 @@ par_length(char *data)
 }
 
 int
-get_expr(struct prog_info *pi, char *data, int *value)
+get_expr(struct prog_info *pi, char *data, int64_t *value)
 {
 	/* Definition */
 	int ok, end, i, count, first_flag, length, function;
diff --git a/src/map.c b/src/map.c
index c28638d..ce3fdb0 100644
--- a/src/map.c
+++ b/src/map.c
@@ -27,6 +27,7 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <inttypes.h>
 #include "avra.h"
 #include "args.h"
 
@@ -50,13 +51,13 @@ write_map_file(struct prog_info *pi)
 		return;
 	}
 	for (label = pi->first_constant; label; label = label->next)
-		fprintf(fp,"%s%sC\t%04x\t%d\n",label->name,Space(label->name),label->value,label->value);
+		fprintf(fp,"%s%sC\t%04"PRIx64"\t%"PRId64"\n",label->name,Space(label->name),label->value,label->value);
 
 	for (label = pi->first_variable; label; label = label->next)
-		fprintf(fp,"%s%sV\t%04x\t%d\n",label->name,Space(label->name),label->value,label->value);
+		fprintf(fp,"%s%sV\t%04"PRIx64"\t%"PRId64"\n",label->name,Space(label->name),label->value,label->value);
 
 	for (label = pi->first_label; label; label = label->next)
-		fprintf(fp,"%s%sL\t%04x\t%d\n",label->name,Space(label->name),label->value,label->value);
+		fprintf(fp,"%s%sL\t%04"PRIx64"\t%"PRId64"\n",label->name,Space(label->name),label->value,label->value);
 
 	fprintf(fp,"\n");
 	fclose(fp);
diff --git a/src/mnemonic.c b/src/mnemonic.c
index a51871a..8ad46a8 100644
--- a/src/mnemonic.c
+++ b/src/mnemonic.c
@@ -346,7 +346,7 @@ int
 parse_mnemonic(struct prog_info *pi)
 {
 	int mnemonic;
-	int i;
+	int64_t i;
 	int opcode = 0;
 	int opcode2 = 0;
 	int instruction_long = False;
@@ -734,7 +734,7 @@ get_register(struct prog_info *pi, char *data)
 }
 
 int
-get_bitnum(struct prog_info *pi, char *data, int *ret)
+get_bitnum(struct prog_info *pi, char *data, int64_t *ret)
 {
 	if (!get_expr(pi, data, ret))
 		return (False);
diff --git a/tests/regression/issue53-int64-expression/test.asm b/tests/regression/issue53-int64-expression/test.asm
new file mode 100644
index 0000000..4d4a155
--- /dev/null
+++ b/tests/regression/issue53-int64-expression/test.asm
@@ -0,0 +1,32 @@
+.device atmega168
+
+.equ F_CPU = 16000000
+
+.macro delay1
+	.set cycles = @0 * (F_CPU / 1000000)
+	.dw cycles
+	.if cycles != 16000
+	.error "error in calculation"
+	.endif
+.endmacro
+
+.macro delay2
+	.set cycles = (@0 * F_CPU) / 1000000
+	.dw cycles
+	.if cycles != 16000
+	.error "error in calculation"
+	.endif
+.endmacro
+
+.macro delay3
+	.set cycles = ( ( @0 * F_CPU ) / 1000000 )
+	.dw cycles
+	.if cycles != 16000
+	.error "error in calculation"
+	.endif
+.endmacro
+
+nop
+delay1 1000
+delay2 1000
+delay3 1000
diff --git a/tests/regression/issue53-int64-expression/test.hex.expected b/tests/regression/issue53-int64-expression/test.hex.expected
new file mode 100644
index 0000000..9c6d6b4
--- /dev/null
+++ b/tests/regression/issue53-int64-expression/test.hex.expected
@@ -0,0 +1,3 @@
+:020000020000FC
+:080000000000803E803E803EBE
+:00000001FF