diff --git a/makefile b/makefile
index 9791cd9e23f..f04d95d4d98 100644
--- a/makefile
+++ b/makefile
@@ -285,7 +285,7 @@ endif
 endif
 
 # 64-bit builds get a '64' suffix
-ifdef PTR64
+ifeq ($(PTR64),1)
 SUFFIX64 = 64
 endif
 
@@ -345,7 +345,7 @@ DEFS += -DLSB_FIRST
 endif
 
 # define PTR64 if we are a 64-bit target
-ifdef PTR64
+ifeq ($(PTR64),1)
 DEFS += -DPTR64
 endif
 
diff --git a/src/emu/cpu/cpu.mak b/src/emu/cpu/cpu.mak
index ea0037e5f3f..7ff4152d4c0 100644
--- a/src/emu/cpu/cpu.mak
+++ b/src/emu/cpu/cpu.mak
@@ -44,7 +44,7 @@ DRCDEPS = \
 # fixme - need to make this work for other target architectures (PPC)
 
 ifndef FORCE_DRC_C_BACKEND
-ifdef PTR64
+ifeq ($(PTR64),1)
 
 DRCOBJ += \
 	$(CPUOBJ)/drcbex64.o \
diff --git a/src/osd/sdl/sdl.mak b/src/osd/sdl/sdl.mak
index 0d2b325ef3c..81d14693ab8 100644
--- a/src/osd/sdl/sdl.mak
+++ b/src/osd/sdl/sdl.mak
@@ -172,7 +172,7 @@ ifdef BIGENDIAN
 ifdef SYMBOLS
 CCOMFLAGS += -mlong-branch
 endif	# SYMBOLS
-ifdef PTR64
+ifeq ($(PTR64),1)
 CCOMFLAGS += -arch ppc64
 LDFLAGS += -arch ppc64
 else
@@ -180,7 +180,7 @@ CCOMFLAGS += -arch ppc
 LDFLAGS += -arch ppc
 endif
 else	# BIGENDIAN
-ifdef PTR64
+ifeq ($(PTR64),1)
 CCOMFLAGS += -arch x86_64
 LDFLAGS += -arch x86_64
 else
@@ -324,7 +324,7 @@ SUPPORTSM32M64 = 1
 endif
 
 ifeq ($(SUPPORTSM32M64),1)
-ifdef PTR64
+ifeq ($(PTR64),1)
 CCOMFLAGS += -m64
 LDFLAGS += -m64
 else
diff --git a/src/osd/windows/windows.mak b/src/osd/windows/windows.mak
index 21d6efeb9a3..8c24fd291d6 100644
--- a/src/osd/windows/windows.mak
+++ b/src/osd/windows/windows.mak
@@ -136,7 +136,7 @@ AR += /LTCG
 endif
 
 # disable warnings and link against bufferoverflowu for 64-bit targets
-ifdef PTR64
+ifeq ($(PTR64),1)
 CCOMFLAGS += /wd4267
 LIBS += -lbufferoverflowu
 endif
@@ -221,7 +221,7 @@ endif
 CCOMFLAGS += -include $(WINSRC)/winprefix.h
 
 # for 32-bit apps, add unicows for Unicode support on Win9x
-ifndef PTR64
+ifneq ($(PTR64),1)
 LIBS += -lunicows
 endif