diff --git a/vlib/builtin/builtin.v b/vlib/builtin/builtin.v
index cdba78038c..5c243da67d 100644
--- a/vlib/builtin/builtin.v
+++ b/vlib/builtin/builtin.v
@@ -137,7 +137,9 @@ pub fn malloc(n int) byteptr {
 	}
 	$if prealloc {
 		res := g_m2_ptr
-		g_m2_ptr += n
+		unsafe {
+			g_m2_ptr += n
+		}
 		nr_mallocs++
 		return res
 	} $else {
diff --git a/vlib/net/socket.v b/vlib/net/socket.v
index 5c21e12253..0b58a66a45 100644
--- a/vlib/net/socket.v
+++ b/vlib/net/socket.v
@@ -234,7 +234,9 @@ pub fn (s Socket) send(buf byteptr, len int) ?int {
 		if dlen <= 0 {
 			break
 		}
-		dptr += sbytes
+		unsafe {
+			dptr += sbytes
+		}
 	}
 	return len
 }
diff --git a/vlib/picohttpparser/misc.v b/vlib/picohttpparser/misc.v
index 1ed6dfafb3..2610925693 100644
--- a/vlib/picohttpparser/misc.v
+++ b/vlib/picohttpparser/misc.v
@@ -1,12 +1,6 @@
 module picohttpparser
 
-[inline]
-fn cpy_str(dst byteptr, src string) int {
-	C.memcpy(dst, src.str, src.len)
-	return src.len
-}
-
-[inline]
+[inline] [unsafe_fn]
 fn cpy(dst, src byteptr, len int) int {
 	C.memcpy(dst, src, len)
 	return len
diff --git a/vlib/picohttpparser/response.v b/vlib/picohttpparser/response.v
index b8819dc74a..4e3f61fa75 100644
--- a/vlib/picohttpparser/response.v
+++ b/vlib/picohttpparser/response.v
@@ -9,87 +9,99 @@ pub mut:
 	buf byteptr
 }
 
+[inline] [unsafe_fn]
+fn (mut r Response) write_str(s string) {
+	unsafe {
+		C.memcpy(r.buf, s.str, s.len)
+		r.buf += s.len
+	}
+}
+
 [inline]
 pub fn (mut r Response) http_ok() &Response {
-	r.buf += cpy_str(r.buf, "HTTP/1.1 200 OK\r\n")
+	r.write_str("HTTP/1.1 200 OK\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) header(k, v string) &Response {
-	r.buf += cpy_str(r.buf, k)
-	r.buf += cpy_str(r.buf, ": ")
-	r.buf += cpy_str(r.buf, v)
-	r.buf += cpy_str(r.buf, "\r\n")
+	r.write_str(k)
+	r.write_str(": ")
+	r.write_str(v)
+	r.write_str("\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) header_date() &Response {
-	r.buf += cpy_str(r.buf, "Date: ")
-	r.buf += cpy(r.buf, r.date, 29)
-	r.buf += cpy_str(r.buf, "\r\n")
+	r.write_str("Date: ")
+	unsafe {
+		r.buf += cpy(r.buf, r.date, 29)
+	}
+	r.write_str("\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) header_server() &Response {
-	r.buf += cpy_str(r.buf, "Server: V\r\n")
+	r.write_str("Server: V\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) content_type(s string) &Response {
-	r.buf += cpy_str(r.buf, "Content-Type: ")
-	r.buf += cpy_str(r.buf, s)
-	r.buf += cpy_str(r.buf, "\r\n")
+	r.write_str("Content-Type: ")
+	r.write_str(s)
+	r.write_str("\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) html() &Response {
-	r.buf += cpy_str(r.buf, "Content-Type: text/html\r\n")
+	r.write_str("Content-Type: text/html\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) plain() &Response {
-	r.buf += cpy_str(r.buf, "Content-Type: text/plain\r\n")
+	r.write_str("Content-Type: text/plain\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) json() &Response {
-	r.buf += cpy_str(r.buf, "Content-Type: application/json\r\n")
+	r.write_str("Content-Type: application/json\r\n")
 	return r
 }
 
 [inline]
 pub fn (mut r Response) body(body string) {
-	r.buf += cpy_str(r.buf, "Content-Length: ")
-	r.buf += C.u64toa(r.buf, body.len)
-	r.buf += cpy_str(r.buf, "\r\n\r\n")
-	r.buf += cpy_str(r.buf, body)
+	r.write_str("Content-Length: ")
+	unsafe {
+		r.buf += C.u64toa(r.buf, body.len)
+	}
+	r.write_str("\r\n\r\n")
+	r.write_str(body)
 }
 
 [inline]
 pub fn (mut r Response) http_404() {
-	r.buf += cpy_str(r.buf, 'HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\n\r\n')
+	r.write_str('HTTP/1.1 404 Not Found\r\nContent-Length: 0\r\n\r\n')
 }
 
 [inline]
 pub fn (mut r Response) http_405() {
-	r.buf += cpy_str(r.buf, 'HTTP/1.1 405 Method Not Allowed\r\nContent-Length: 0\r\n\r\n')
+	r.write_str('HTTP/1.1 405 Method Not Allowed\r\nContent-Length: 0\r\n\r\n')
 }
 
 [inline]
 pub fn (mut r Response) http_500() {
-	r.buf += cpy_str(r.buf, 'HTTP/1.1 500 Internal Server Error\r\nContent-Length: 0\r\n\r\n')
+	r.write_str('HTTP/1.1 500 Internal Server Error\r\nContent-Length: 0\r\n\r\n')
 }
 
 [inline]
 pub fn (mut r Response) raw(response string) {
-	r.buf += cpy_str(r.buf, response)
+	r.write_str(response)
 }
 
 [inline]
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 0e939f61bd..7958e01cba 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1505,7 +1505,7 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 			ast.PrefixExpr {
 				// Do now allow `*x = y` outside `unsafe`
 				if left.op == .mul && !c.inside_unsafe {
-					c.error('modifying variables via deferencing can only be done in `unsafe` blocks',
+					c.error('modifying variables via dereferencing can only be done in `unsafe` blocks',
 						assign_stmt.pos)
 				}
 			}
@@ -1515,6 +1515,11 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		right_type_unwrapped := c.unwrap_generic(right_type)
 		left_sym := c.table.get_type_symbol(left_type_unwrapped)
 		right_sym := c.table.get_type_symbol(right_type_unwrapped)
+		if (left_type.is_ptr() || left_sym.is_pointer()) &&
+			assign_stmt.op !in [.assign, .decl_assign] && !c.inside_unsafe {
+			c.error('pointer arithmetic is only allowed in `unsafe` blocks',
+				assign_stmt.pos)
+		}
 		// Single side check
 		match assign_stmt.op {
 			.assign {} // No need to do single side check for =. But here put it first for speed.
@@ -2582,6 +2587,10 @@ pub fn (mut c Checker) postfix_expr(node ast.PostfixExpr) table.Type {
 	} else {
 		c.fail_if_immutable(node.expr)
 	}
+	if (typ.is_ptr() || typ_sym.is_pointer()) && !c.inside_unsafe {
+		c.error('pointer arithmetic is only allowed in `unsafe` blocks',
+			node.pos)
+	}
 	return typ
 }
 
diff --git a/vlib/v/tests/ptr_arithmetic_test.v b/vlib/v/tests/ptr_arithmetic_test.v
new file mode 100644
index 0000000000..47b8c0903b
--- /dev/null
+++ b/vlib/v/tests/ptr_arithmetic_test.v
@@ -0,0 +1,16 @@
+fn test_ptr_arithmetic(){
+	v := 4
+	mut p := &v
+	unsafe {
+		p++
+		p += 2
+	}
+	p = p - 1 // not caught yet
+	
+	// byteptr, voidptr, charptr are handled differently
+	mut q := byteptr(1)
+	unsafe {
+		q -= 2
+	}
+	q = q + 1 // not caught yet
+}