diff --git a/share/mk/bsd.progs.mk b/share/mk/bsd.progs.mk
index ab527089c807..3efa691f45a8 100644
--- a/share/mk/bsd.progs.mk
+++ b/share/mk/bsd.progs.mk
@@ -84,6 +84,25 @@ $v =
 # tell progs.mk we might want to install things
 PROGS_TARGETS+= checkdpadd clean cleandepend cleandir depend install
 
+# Find common sources among the PROGS and depend on them before building
+# anything.  This allows parallelization without them each fighting over
+# the same objects.
+_PROGS_COMMON_SRCS=
+_PROGS_ALL_SRCS=
+.for p in ${PROGS}
+.for s in ${SRCS.${p}}
+.if ${_PROGS_ALL_SRCS:M${s}} && !${_PROGS_COMMON_SRCS:M${s}}
+_PROGS_COMMON_SRCS+=	${s}
+.else
+_PROGS_ALL_SRCS+=	${s}
+.endif
+.endfor
+.endfor
+.if !empty(_PROGS_COMMON_SRCS)
+_PROGS_COMMON_OBJS=	${_PROGS_COMMON_SRCS:N*.h:R:S/$/.o/g}
+${PROGS}: ${_PROGS_COMMON_OBJS}
+.endif
+
 .for p in ${PROGS}
 .if defined(PROGS_CXX) && !empty(PROGS_CXX:M$p)
 # bsd.prog.mk may need to know this