diff --git a/control/magma_internal.h b/control/magma_internal.h
index 7af16a5..0133e44 100644
--- a/control/magma_internal.h
+++ b/control/magma_internal.h
@@ -33,7 +33,7 @@
     // functions where Microsoft fails to provide C99 standard
     // (only with Microsoft, not with nvcc on Windows)
     // in both magma_internal.h and testings.h
-    #ifndef __NVCC__
+    #if !defined(__NVCC__) && !defined(__clang__)
 
         #include <float.h>
         #define copysign(x,y) _copysign(x,y)
@@ -43,6 +43,9 @@
         // note _snprintf has slightly different semantics than snprintf
         #define snprintf _snprintf
 
+    #elif !defined(__NVCC__)
+        // make sure this actually uses the C version and not the C++ overloads
+        #define copysign(x,y) copysign((double)x,(double)y)
     #endif
 
 #else