diff --git a/src/buspirate.c b/src/buspirate.c
index e4d09104..8c3ee1a9 100644
--- a/src/buspirate.c
+++ b/src/buspirate.c
@@ -669,7 +669,7 @@ static int buspirate_start_spi_mode_ascii(const PROGRAMMER *pgm) {
 		if (rcvd == NULL) {
 			return -1;
 		}
-		if (strstr(rcvd, "Normal (H=3.3V, L=GND)")) {
+		if (str_contains(rcvd, "Normal (H=3.3V, L=GND)")) {
 			/* BP firmware 2.1 defaults to Open-drain output.
 			 * That doesn't work on my board, even with pull-up
 			 * resistors. Select 3.3V output mode instead. */
diff --git a/src/developer_opts.c b/src/developer_opts.c
index 5f60784a..ccb25d8b 100644
--- a/src/developer_opts.c
+++ b/src/developer_opts.c
@@ -345,7 +345,7 @@ int dev_message(int msglvl, const char *fmt, ...) {
 int dev_has_subsstr_comms(const LISTID comms, const char *subs) {
   if(comms)
     for(LNODEID ln=lfirst(comms); ln; ln=lnext(ln))
-       if(strstr((char *) ldata(ln), subs))
+       if(str_contains((char *) ldata(ln), subs))
          return 1;
   return 0;
 }
diff --git a/src/usb_libusb.c b/src/usb_libusb.c
index 605828ee..24305b9c 100644
--- a/src/usb_libusb.c
+++ b/src/usb_libusb.c
@@ -155,7 +155,7 @@ static int usbdev_open(const char *port, union pinfo pinfo, union filedescriptor
 		   * whether we have to search for a HID interface
 		   * below.
 		   */
-		  if(strstr(product, "CMSIS-DAP") != NULL)
+		  if(str_contains(product, "CMSIS-DAP"))
 		  {
 		      pinfo.usbinfo.flags |= PINFO_FL_USEHID;
 		      /* The JTAGICE3 running the CMSIS-DAP firmware doesn't
@@ -163,7 +163,7 @@ static int usbdev_open(const char *port, union pinfo pinfo, union filedescriptor
 		      fd->usb.eep = 0;
 		  }
 
-		  if(strstr(product, "mEDBG") != NULL)
+		  if(str_contains(product, "mEDBG"))
 		  {
 		      /* The AVR Xplained Mini uses different endpoints. */
 		      fd->usb.rep = 0x81;