diff --git a/Config/defs.mk.in b/Config/defs.mk.in
index a3af5aad9..4a055c61e 100644
--- a/Config/defs.mk.in
+++ b/Config/defs.mk.in
@@ -96,3 +96,9 @@ FUNCTIONS_INSTALL='$(FUNCTIONS_INSTALL)' tzsh='$(tzsh)'
 
 # override built-in suffix list
 .SUFFIXES:
+
+# parallel build is not supported (pmake, gmake)
+.NOTPARALLEL:
+
+# parallel build is not supported (dmake)
+.NO_PARALLEL: