diff --git a/include/assimp/defs.h b/include/assimp/defs.h
index 4fcfb9664..e1aaafd44 100644
--- a/include/assimp/defs.h
+++ b/include/assimp/defs.h
@@ -292,7 +292,7 @@ typedef unsigned int ai_uint;
 #ifdef __cplusplus
 constexpr ai_real ai_epsilon = (ai_real) 1e-6;
 #else
-const ai_real ai_epsilon = (ai_real) 1e-6;
+#define ai_epsilon ((ai_real)1e-6)
 #endif
 
 /* Support for big-endian builds */
@@ -343,4 +343,4 @@ const ai_real ai_epsilon = (ai_real) 1e-6;
 
 #define AI_COUNT_OF(X) (sizeof(X) / sizeof((X)[0]))
 
-#endif // !! AI_DEFINES_H_INC
+#endif // !! AI_DEFINES_H_INC
\ No newline at end of file