diff --git a/build/modmake.rules.in b/build/modmake.rules.in
index cd0247b8b1..182af4aa29 100644
--- a/build/modmake.rules.in
+++ b/build/modmake.rules.in
@@ -29,6 +29,7 @@ MODINSTDIR = @modinstdir@
 DYLD_LIBRARY_PATH=@libdir@:$DYLD_LIBRARY_PATH
 LD_LIBRARY_PATH=@libdir@:$LD_LIBRARY_PATH
 OSARCH=`uname -s`
+DYNAMIC_LIB_EXTEN = @DYNAMIC_LIB_EXTEN@
 LIBTOOL_LIB_EXTEN = @LIBTOOL_LIB_EXTEN@
 SOLINK = @SOLINK@