diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index ebc5c0b97..63c7adad7 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -6485,6 +6485,10 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_CheckProximity)
 		if (mo == ref) //Don't count self.
 			continue;
 
+		// no unmorphed versions of currently morphed players.
+		if (mo->flags & MF_UNMORPHED)
+			continue;
+
 		//Check inheritance for the classname. Taken partly from CheckClass DECORATE function.
 		if (flags & CPXF_ANCESTOR)
 		{