diff --git a/evaluate.c b/evaluate.c
index 1533730..815e7e1 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -2090,7 +2090,8 @@ static struct symbol *evaluate_sizeof(struct expression *expr)
 	size = type->bit_size;
 
 	if (size < 0 && is_void_type(type)) {
-		warning(expr->pos, "expression using sizeof(void)");
+		if (Wpointer_arith)
+			warning(expr->pos, "expression using sizeof(void)");
 		size = bits_in_char;
 	}
 
@@ -2101,7 +2102,8 @@ static struct symbol *evaluate_sizeof(struct expression *expr)
 	}
 
 	if (is_function(type->ctype.base_type)) {
-		warning(expr->pos, "expression using sizeof on a function");
+		if (Wpointer_arith)
+			warning(expr->pos, "expression using sizeof on a function");
 		size = bits_in_char;
 	}
 
diff --git a/lib.c b/lib.c
index 69b5ab8..ed4a74f 100644
--- a/lib.c
+++ b/lib.c
@@ -234,6 +234,7 @@ int Wnon_pointer_null = 1;
 int Wold_initializer = 1;
 int Wone_bit_signed_bitfield = 1;
 int Wparen_string = 0;
+int Wpointer_arith = 0;
 int Wptr_subtraction_blows = 0;
 int Wreturn_void = 0;
 int Wshadow = 0;
@@ -453,6 +454,7 @@ static const struct warning {
 	{ "return-void", &Wreturn_void },
 	{ "shadow", &Wshadow },
 	{ "sizeof-bool", &Wsizeof_bool },
+	{ "pointer-arith", &Wpointer_arith },
 	{ "transparent-union", &Wtransparent_union },
 	{ "typesign", &Wtypesign },
 	{ "undef", &Wundef },
diff --git a/lib.h b/lib.h
index 0838342..a86615b 100644
--- a/lib.h
+++ b/lib.h
@@ -120,6 +120,7 @@ extern int Wnon_pointer_null;
 extern int Wold_initializer;
 extern int Wone_bit_signed_bitfield;
 extern int Wparen_string;
+extern int Wpointer_arith;
 extern int Wptr_subtraction_blows;
 extern int Wreturn_void;
 extern int Wshadow;
diff --git a/sparse.1 b/sparse.1
index acdce53..53eff87 100644
--- a/sparse.1
+++ b/sparse.1
@@ -265,6 +265,19 @@ initializer.  GCC allows this syntax as an extension.  With
 Sparse does not issue these warnings by default.
 .
 .TP
+.B \-Wpointer\-arith
+Warn about anything that depends on the \fBsizeof\fR a void or function type.
+
+C99 does not allow the \fBsizeof\fR operator to be applied to function types
+or to incomplete types such as void. GCC allows \fBsizeof\fR to be applied to
+these types as an extension and assigns these types a size of \fI1\fR. With
+\fB\-pointer\-arith\fR, Sparse will warn about pointer arithmetic on void
+or function pointers, as well as expressions which directly apply the
+\fBsizeof\fR operator to void or function types.
+
+Sparse does not issue these warnings by default.
+.
+.TP
 .B \-Wptr\-subtraction\-blows
 Warn when subtracting two pointers to a type with a non-power-of-two size.