diff --git a/src/zm.h b/src/zm.h
index 02ce6523b..78f7bca82 100644
--- a/src/zm.h
+++ b/src/zm.h
@@ -27,6 +27,13 @@ extern "C"
 
 #include "zm_config.h"
 
+extern "C"
+{
+#if !HAVE_DECL_ROUND
+double round(double);
+#endif
+}
+
 // Structure used for storing the results of the subtraction
 // of one struct timeval from another
 
diff --git a/src/zm_image.h b/src/zm_image.h
index 901584453..bc1d23549 100644
--- a/src/zm_image.h
+++ b/src/zm_image.h
@@ -30,10 +30,6 @@
 
 extern "C"
 {
-#if !HAVE_DECL_ROUND
-double round(double);
-#endif
-
 #include "zm_jpeg.h"
 }