diff --git a/src/target/breakpoints.c b/src/target/breakpoints.c
index 889865185..dd672b9fe 100644
--- a/src/target/breakpoints.c
+++ b/src/target/breakpoints.c
@@ -178,54 +178,61 @@ breakpoint_t* breakpoint_find(target_t *target, uint32_t address)
 	return NULL;
 }
 
-int watchpoint_add(target_t *target, uint32_t address, uint32_t length, enum watchpoint_rw rw, uint32_t value, uint32_t mask)
+int watchpoint_add(target_t *target, uint32_t address, uint32_t length,
+		enum watchpoint_rw rw, uint32_t value, uint32_t mask)
 {
 	watchpoint_t *watchpoint = target->watchpoints;
 	watchpoint_t **watchpoint_p = &target->watchpoints;
 	int retval;
+	char *reason;
 
 	while (watchpoint)
 	{
-		if (watchpoint->address == address)
+		if (watchpoint->address == address) {
+			if (watchpoint->length != length
+					|| watchpoint->value != value
+					|| watchpoint->mask != mask
+					|| watchpoint->rw != rw) {
+				LOG_ERROR("address 0x%8.8" PRIx32
+						"already has watchpoint %d",
+						address, watchpoint->unique_id);
+				return ERROR_FAIL;
+			}
+
+			/* ignore duplicate watchpoint */
 			return ERROR_OK;
+		}
 		watchpoint_p = &watchpoint->next;
 		watchpoint = watchpoint->next;
 	}
 
-	(*watchpoint_p) = malloc(sizeof(watchpoint_t));
+	(*watchpoint_p) = calloc(1, sizeof(watchpoint_t));
 	(*watchpoint_p)->address = address;
 	(*watchpoint_p)->length = length;
 	(*watchpoint_p)->value = value;
 	(*watchpoint_p)->mask = mask;
 	(*watchpoint_p)->rw = rw;
-	(*watchpoint_p)->set = 0;
-	(*watchpoint_p)->next = NULL;
 	(*watchpoint_p)->unique_id = bpwp_unique_id++;
 
-	if ((retval = target_add_watchpoint(target, *watchpoint_p)) != ERROR_OK)
-	{
-		switch (retval)
-		{
-			case ERROR_TARGET_RESOURCE_NOT_AVAILABLE:
-				LOG_INFO("can't add %s watchpoint, resource not available (WPID: %d)",
-					 watchpoint_rw_strings[(*watchpoint_p)->rw],
-					 (*watchpoint_p)->unique_id );
-				free (*watchpoint_p);
-				*watchpoint_p = NULL;
-				return retval;
-				break;
-			case ERROR_TARGET_NOT_HALTED:
-				LOG_INFO("can't add watchpoint while target is running (WPID: %d)",
-						 (*watchpoint_p)->unique_id );
-				free (*watchpoint_p);
-				*watchpoint_p = NULL;
-				return retval;
-				break;
-			default:
-				LOG_ERROR("unknown error");
-				exit(-1);
-				break;
-		}
+	retval = target_add_watchpoint(target, *watchpoint_p);
+	switch (retval) {
+	case ERROR_OK:
+		break;
+	case ERROR_TARGET_RESOURCE_NOT_AVAILABLE:
+		reason = "resource not available";
+		goto bye;
+	case ERROR_TARGET_NOT_HALTED:
+		reason = "target running";
+		goto bye;
+	default:
+		reason = "unrecognized error";
+bye:
+		LOG_ERROR("can't add %s watchpoint at 0x%8.8" PRIx32 ", %s",
+			 watchpoint_rw_strings[(*watchpoint_p)->rw],
+			 address, reason);
+		free (*watchpoint_p);
+		*watchpoint_p = NULL;
+		return retval;
 	}
 
 	LOG_DEBUG("added %s watchpoint at 0x%8.8" PRIx32 " of length 0x%8.8x (WPID: %d)",
diff --git a/src/target/breakpoints.h b/src/target/breakpoints.h
index b75aae624..91459669e 100644
--- a/src/target/breakpoints.h
+++ b/src/target/breakpoints.h
@@ -49,7 +49,7 @@ typedef struct breakpoint_s
 typedef struct watchpoint_s
 {
 	uint32_t address;
-	int length;
+	uint32_t length;
 	uint32_t mask;
 	uint32_t value;
 	enum watchpoint_rw rw;
diff --git a/src/target/cortex_m3.c b/src/target/cortex_m3.c
index eb37add3d..51481a988 100644
--- a/src/target/cortex_m3.c
+++ b/src/target/cortex_m3.c
@@ -1199,7 +1199,7 @@ cortex_m3_add_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 	unsigned mask;
 
 	for (mask = 0; mask < 16; mask++) {
-		if ((1 << mask) == watchpoint->length)
+		if ((1u << mask) == watchpoint->length)
 			break;
 	}
 	if (mask == 16) {
diff --git a/src/target/target.c b/src/target/target.c
index 2a66fcf10..55fc2c823 100644
--- a/src/target/target.c
+++ b/src/target/target.c
@@ -2988,7 +2988,8 @@ static int handle_wp_command(struct command_context_s *cmd_ctx, char *cmd, char
 		break;
 
 	default:
-		command_print(cmd_ctx, "usage: wp <address> <length> [r/w/a] [value] [mask]");
+		command_print(cmd_ctx, "usage: wp [address length "
+				"[(r|w|a) [value [mask]]]]");
 		return ERROR_COMMAND_SYNTAX_ERROR;
 	}