diff --git a/modules/preprocs/yapp/Makefile.inc b/modules/preprocs/yapp/Makefile.inc
index bfb6e090..59e1c476 100644
--- a/modules/preprocs/yapp/Makefile.inc
+++ b/modules/preprocs/yapp/Makefile.inc
@@ -18,8 +18,11 @@ TESTS += \
 
 EXTRA_DIST += \
 	src/preprocs/yapp/tests/define.asm \
-	src/preprocs/yapp/tests/define.pre
+	src/preprocs/yapp/tests/define.pre \
+	src/preprocs/yapp/tests/ifdef.asm \
+	src/preprocs/yapp/tests/ifdef.pre \
 
 CLEANFILES += \
-	define.yp
+	define.yp \
+	ifdef.yp
 
diff --git a/modules/preprocs/yapp/tests/ifdef.asm b/modules/preprocs/yapp/tests/ifdef.asm
new file mode 100644
index 00000000..b9d7807e
--- /dev/null
+++ b/modules/preprocs/yapp/tests/ifdef.asm
@@ -0,0 +1,13 @@
+%ifdef foo
+	mov	ax, foo
+%endif
+%ifdef bar
+	mov	ax, bar
+%endif
+%define foo 5
+%ifdef foo
+	mov	ax, foo
+%endif
+%ifdef bar
+	mov	ax, bar
+%endif
diff --git a/modules/preprocs/yapp/tests/ifdef.pre b/modules/preprocs/yapp/tests/ifdef.pre
new file mode 100644
index 00000000..b7aa1897
--- /dev/null
+++ b/modules/preprocs/yapp/tests/ifdef.pre
@@ -0,0 +1,10 @@
+
+%line 3+1 ./src/preprocs/yapp/tests/ifdef.asm
+
+%line 6+1 ./src/preprocs/yapp/tests/ifdef.asm
+
+
+	mov	ax, 5
+
+
+%line 13+1 ./src/preprocs/yapp/tests/ifdef.asm
diff --git a/src/preprocs/yapp/Makefile.inc b/src/preprocs/yapp/Makefile.inc
index bfb6e090..59e1c476 100644
--- a/src/preprocs/yapp/Makefile.inc
+++ b/src/preprocs/yapp/Makefile.inc
@@ -18,8 +18,11 @@ TESTS += \
 
 EXTRA_DIST += \
 	src/preprocs/yapp/tests/define.asm \
-	src/preprocs/yapp/tests/define.pre
+	src/preprocs/yapp/tests/define.pre \
+	src/preprocs/yapp/tests/ifdef.asm \
+	src/preprocs/yapp/tests/ifdef.pre \
 
 CLEANFILES += \
-	define.yp
+	define.yp \
+	ifdef.yp
 
diff --git a/src/preprocs/yapp/tests/ifdef.asm b/src/preprocs/yapp/tests/ifdef.asm
new file mode 100644
index 00000000..b9d7807e
--- /dev/null
+++ b/src/preprocs/yapp/tests/ifdef.asm
@@ -0,0 +1,13 @@
+%ifdef foo
+	mov	ax, foo
+%endif
+%ifdef bar
+	mov	ax, bar
+%endif
+%define foo 5
+%ifdef foo
+	mov	ax, foo
+%endif
+%ifdef bar
+	mov	ax, bar
+%endif
diff --git a/src/preprocs/yapp/tests/ifdef.pre b/src/preprocs/yapp/tests/ifdef.pre
new file mode 100644
index 00000000..b7aa1897
--- /dev/null
+++ b/src/preprocs/yapp/tests/ifdef.pre
@@ -0,0 +1,10 @@
+
+%line 3+1 ./src/preprocs/yapp/tests/ifdef.asm
+
+%line 6+1 ./src/preprocs/yapp/tests/ifdef.asm
+
+
+	mov	ax, 5
+
+
+%line 13+1 ./src/preprocs/yapp/tests/ifdef.asm