diff --git a/src/operators/validate_dtd.h b/src/operators/validate_dtd.h
index e69e280a3e..4056c38377 100644
--- a/src/operators/validate_dtd.h
+++ b/src/operators/validate_dtd.h
@@ -28,6 +28,7 @@
 #include <utility>
 
 #include "src/operators/operator.h"
+#include "validate_schema.h"
 
 
 namespace modsecurity {
@@ -62,40 +63,22 @@ class ValidateDTD : public Operator {
 
 
     static void error_runtime(void *ctx, const char *msg, ...) {
-        const Transaction *t = reinterpret_cast<Transaction *>(ctx);
-        char buf[1024];
-        std::string s;
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        ValidateSchema::callback_func(ctx, ValidateSchema::log_msg, ValidateSchema::PREFIX_ERROR, msg, args);
         va_end(args);
-
-        if (len > 0) {
-            s = "XML Error: " + std::string(buf);
-        }
-        ms_dbg_a(t, 4, s);
     }
 
 
     static void warn_runtime(void *ctx, const char *msg, ...) {
-        const Transaction *t = reinterpret_cast<Transaction *>(ctx);
-        char buf[1024];
-        std::string s;
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        ValidateSchema::callback_func(ctx, ValidateSchema::log_msg, ValidateSchema::PREFIX_WARNING, msg, args);
         va_end(args);
-
-        if (len > 0) {
-            s = "XML Warning: " + std::string(buf);
-        }
-        ms_dbg_a(t, 4, s);
     }
 
 
-    static void null_error(void *ctx, const char *msg, ...) { // cppcheck-suppress[constParameterPointer,constParameterCallback]
+    static void null_error(void *, const char *, ...) { // cppcheck-suppress[constParameterPointer,constParameterCallback]
     }
 
  private:
diff --git a/src/operators/validate_schema.h b/src/operators/validate_schema.h
index 510cfc65e3..72d5a679cc 100644
--- a/src/operators/validate_schema.h
+++ b/src/operators/validate_schema.h
@@ -45,71 +45,61 @@ class ValidateSchema : public Operator {
 
 
     static void error_load(void *ctx, const char *msg, ...) {
-        std::string *t = reinterpret_cast<std::string *>(ctx);
-        char buf[1024];
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        callback_func(ctx, append_msg, PREFIX_ERROR, msg, args);
         va_end(args);
-
-        if (len > 0) {
-            t->append("XML Error: " + std::string(buf));
-        }
     }
 
 
     static void warn_load(void *ctx, const char *msg, ...) {
-        std::string *t = reinterpret_cast<std::string *>(ctx);
-        char buf[1024];
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        callback_func(ctx, append_msg, PREFIX_WARNING, msg, args);
         va_end(args);
-
-        if (len > 0) {
-            t->append("XML Warning: " + std::string(buf));
-        }
     }
 
 
     static void error_runtime(void *ctx, const char *msg, ...) {
-        const Transaction *t = reinterpret_cast<Transaction *>(ctx);
-        char buf[1024];
-        std::string s;
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        callback_func(ctx, log_msg, PREFIX_ERROR, msg, args);
         va_end(args);
-
-        if (len > 0) {
-            s = "XML Error: " + std::string(buf);
-        }
-        ms_dbg_a(t, 4, s);
     }
 
 
     static void warn_runtime(void *ctx, const char *msg, ...) {
-        const Transaction *t = reinterpret_cast<Transaction *>(ctx);
-        char buf[1024];
-        std::string s;
         va_list args;
-
         va_start(args, msg);
-        int len = vsnprintf(buf, sizeof(buf), msg, args);
+        callback_func(ctx, log_msg, PREFIX_WARNING, msg, args);
         va_end(args);
+    }
 
-        if (len > 0) {
-            s = "XML Warning: " + std::string(buf);
-        }
-        ms_dbg_a(t, 4, s);
+    static void null_error(void *, const char *, ...) { // cppcheck-suppress[constParameterPointer,constParameterCallback]
     }
 
-    static void null_error(void *ctx, const char *msg, ...) { // cppcheck-suppress[constParameterPointer,constParameterCallback]
+    template<typename Pred>
+    static void callback_func(void *ctx, Pred pred, const char *base_msg, const char *msg, va_list args) {
+        char buf[1024];
+        const auto len = vsnprintf(buf, sizeof(buf), msg, args);
+
+        if (len > 0)
+            pred(ctx, base_msg + std::string(buf));
     }
 
+    static void log_msg(void *ctx, const std::string &msg) {
+        auto t = reinterpret_cast<Transaction *>(ctx);
+        ms_dbg_a(t, 4, msg);
+    }
+
+    static void append_msg(void *ctx, const std::string &msg) {
+        auto s = reinterpret_cast<std::string*>(ctx);
+        s->append(msg);
+    }
+
+    static constexpr auto PREFIX_WARNING = "XML Warning: ";
+    static constexpr auto PREFIX_ERROR = "XML Error: ";
+
  private:
     std::string m_resource;
     std::string m_err;