diff --git a/include/assimp/defs.h b/include/assimp/defs.h
index 406deb5fb..df45525c1 100644
--- a/include/assimp/defs.h
+++ b/include/assimp/defs.h
@@ -299,7 +299,7 @@ typedef unsigned int ai_uint;
 
 /* Numerical limits */
 #ifdef __cplusplus
-constexpr ai_real ai_epsilon = (ai_real) 1e-6;
+inline constexpr ai_real ai_epsilon = (ai_real) 1e-6;
 #else
 #  define ai_epsilon ((ai_real)1e-6)
 #endif