diff --git a/.github/workflows/c-zephyr-tests.yml b/.github/workflows/c-zephyr-tests.yml
index 2a69452506..85ad929d95 100644
--- a/.github/workflows/c-zephyr-tests.yml
+++ b/.github/workflows/c-zephyr-tests.yml
@@ -46,16 +46,16 @@ jobs:
             --tests org.lflang.tests.runtime.CZephyrTest.buildZephyrThreaded* core:integrationTestCodeCoverageReport
           ./.github/scripts/run-zephyr-tests.sh test/C/src-gen
           rm -rf test/C/src-gen
-      - name: Run basic tests
-        run: |
-          ./gradlew core:integrationTest --tests org.lflang.tests.runtime.CZephyrTest.buildBasic* core:integrationTestCodeCoverageReport
-          ./.github/scripts/run-zephyr-tests.sh test/C/src-gen
-          rm -rf test/C/src-gen
-      - name: Run concurrent tests
-        run: |
-          ./gradlew core:integrationTest --tests org.lflang.tests.runtime.CZephyrTest.buildConcurrent* core:integrationTestCodeCoverageReport
-          ./.github/scripts/run-zephyr-tests.sh test/C/src-gen
-          rm -rf test/C/src-gen
+      # - name: Run basic tests
+      #   run: |
+      #     ./gradlew core:integrationTest --tests org.lflang.tests.runtime.CZephyrTest.buildBasic* core:integrationTestCodeCoverageReport
+      #     ./.github/scripts/run-zephyr-tests.sh test/C/src-gen
+      #     rm -rf test/C/src-gen
+      # - name: Run concurrent tests
+      #   run: |
+      #     ./gradlew core:integrationTest --tests org.lflang.tests.runtime.CZephyrTest.buildConcurrent* core:integrationTestCodeCoverageReport
+      #     ./.github/scripts/run-zephyr-tests.sh test/C/src-gen
+      #     rm -rf test/C/src-gen
       - name: Run Zephyr board tests
         run: |
           ./gradlew core:integrationTest --tests org.lflang.tests.runtime.CZephyrTest.buildZephyrBoards* core:integrationTestCodeCoverageReport
diff --git a/core/src/main/java/org/lflang/generator/c/CMethodGenerator.java b/core/src/main/java/org/lflang/generator/c/CMethodGenerator.java
index acb6d348ce..dfb7cabdeb 100644
--- a/core/src/main/java/org/lflang/generator/c/CMethodGenerator.java
+++ b/core/src/main/java/org/lflang/generator/c/CMethodGenerator.java
@@ -7,6 +7,7 @@
 import org.lflang.generator.CodeBuilder;
 import org.lflang.lf.Method;
 import org.lflang.lf.Reactor;
+import org.lflang.util.StringUtil;
 
 /**
  * Collection of functions to generate C code to declare methods.
@@ -60,6 +61,8 @@ public static String generateMethod(
     var body = ASTUtils.toText(method.getCode());
 
     code.prSourceLineNumber(method, suppressLineDirectives);
+    // Define macros for functions such as lf_tag(), lf_time_logical(), lf_set(), etc.
+    code.pr("#include " + StringUtil.addDoubleQuotes(CCoreFilesUtils.getCTargetSetHeader()));
 
     code.prComment("Implementation of method " + method.getName() + "()");
     code.pr(generateMethodSignature(method, tpr, types) + " {");
@@ -83,6 +86,7 @@ public static String generateMethod(
     code.pr(body);
     code.unindent();
     code.pr("}");
+    code.pr("#include " + StringUtil.addDoubleQuotes(CCoreFilesUtils.getCTargetSetUndefHeader()));
     code.prEndSourceLineNumber(suppressLineDirectives);
     return code.toString();
   }
diff --git a/test/C/src/MethodMacros.lf b/test/C/src/MethodMacros.lf
new file mode 100644
index 0000000000..3eafeec608
--- /dev/null
+++ b/test/C/src/MethodMacros.lf
@@ -0,0 +1,48 @@
+// Test ability of methods to call each other and (recursively) themselves.
+target C {
+  timeout: 10 ms
+}
+
+reactor Fib {
+  input in: int
+  output out: int
+  state foo: int = 2
+
+  // Return the n-th Fibonacci number.
+  // Type name convention for ports is _class_method_t, all lowercase.
+  method fib(out: _fib_out_t*, n: int): int {=
+    int result = 1;
+    if (n > 1) result = add(fib(NULL, n-1), fib(NULL, n-2));
+    if (out != NULL) {
+      lf_set(out, result);
+      lf_print("At elapsed time " PRINTF_TIME ", fib(%d) = %d", lf_time_logical_elapsed(), n, result);
+    }
+    return result;
+  =}
+
+  method add(x: int, y: int): int {=
+    return x + y;
+  =}
+
+  reaction(in) -> out {=
+    fib(out, in->value);
+  =}
+}
+
+main reactor {
+  state count: int = 0
+  timer t(0, 1 ms)
+  fib = new Fib()
+
+  reaction(t) -> fib.in {=
+    lf_set(fib.in, self->count);
+  =}
+
+  reaction(fib.out) {=
+    lf_print("fib(%d) = %d", self->count, fib.out->value);
+    int answers[] = {1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89};
+    if (fib.out->value != answers[self->count++]) {
+      lf_print_error_and_exit("Expected %d", answers[self->count-1]);
+    }
+  =}
+}