diff --git a/sample/Makefile.macos b/sample/Makefile.macos
index ba5b6093..b9f4e594 100644
--- a/sample/Makefile.macos
+++ b/sample/Makefile.macos
@@ -10,6 +10,7 @@ CFLAGS=-O2 -F$(MUJOCOPATH) -I$(GLFWROOT)/include -pthread
 CXXFLAGS=$(CFLAGS) -std=c++17 -stdlib=libc++
 ALLFLAGS=$(CXXFLAGS) -L$(GLFWROOT)/lib -Wl,-rpath,$(MUJOCOPATH)
 
+.PHONY: all
 all:
 	clang++ $(ALLFLAGS)    testxml.cc    -framework mujoco        -o testxml
 	clang++ $(ALLFLAGS)    testspeed.cc  -framework mujoco        -o testspeed
diff --git a/sample/Makefile.windows b/sample/Makefile.windows
index 6bbc028a..c6ba0fae 100644
--- a/sample/Makefile.windows
+++ b/sample/Makefile.windows
@@ -8,6 +8,7 @@
 
 COMMON=/O2 /MT /EHsc /arch:AVX /I../include /Fe../bin/
 
+.PHONY: all
 all:
 	cl $(COMMON) testxml.cc                                ../lib/mujoco.lib
 	cl $(COMMON) testspeed.cc                              ../lib/mujoco.lib