diff --git a/src/adiv5_jtagdp.c b/src/adiv5_jtagdp.c
index bb478d1..a460113 100644
--- a/src/adiv5_jtagdp.c
+++ b/src/adiv5_jtagdp.c
@@ -91,8 +91,8 @@ static uint32_t adiv5_jtagdp_low_access(ADIv5_DP_t *dp, uint8_t RnW,
 		ack = response & 0x07;
 	} while(--tries && (ack == JTAGDP_ACK_WAIT));
 
-	if (dp->allow_timeout && (ack == JTAGDP_ACK_WAIT))
-		return 0;
+	if (ack == JTAGDP_ACK_WAIT)
+		raise_exception(EXCEPTION_TIMEOUT, "JTAG-DP ACK timeout");
 
 	if((ack != JTAGDP_ACK_OK))
 		raise_exception(EXCEPTION_ERROR, "JTAG-DP invalid ACK");
diff --git a/src/adiv5_swdp.c b/src/adiv5_swdp.c
index d5193ac..1a6b158 100644
--- a/src/adiv5_swdp.c
+++ b/src/adiv5_swdp.c
@@ -136,8 +136,8 @@ static uint32_t adiv5_swdp_low_access(ADIv5_DP_t *dp, uint8_t RnW,
 		ack = swdptap_seq_in(3);
 	} while(--tries && ack == SWDP_ACK_WAIT);
 
-	if (dp->allow_timeout && (ack == SWDP_ACK_WAIT))
-		return 0;
+	if (ack == SWDP_ACK_WAIT)
+		raise_exception(EXCEPTION_TIMEOUT, "SWDP ACK timeout");
 
 	if(ack == SWDP_ACK_FAULT) {
 		dp->fault = 1;
diff --git a/src/cortexm.c b/src/cortexm.c
index a129a3c..f20f282 100644
--- a/src/cortexm.c
+++ b/src/cortexm.c
@@ -29,6 +29,7 @@
  * There are way too many magic numbers used here.
  */
 #include "general.h"
+#include "exception.h"
 #include "jtagtap.h"
 #include "jtag_scan.h"
 #include "adiv5.h"
@@ -467,12 +468,15 @@ cortexm_reset(struct target_s *target)
 static void
 cortexm_halt_request(struct target_s *target)
 {
-	ADIv5_AP_t *ap = adiv5_target_ap(target);
-
-	ap->dp->allow_timeout = false;
-	target_mem_write32(target, CORTEXM_DHCSR,
-	                   CORTEXM_DHCSR_DBGKEY | CORTEXM_DHCSR_C_HALT |
-	                   CORTEXM_DHCSR_C_DEBUGEN);
+	volatile struct exception e;
+	TRY_CATCH (e, EXCEPTION_TIMEOUT) {
+		target_mem_write32(target, CORTEXM_DHCSR, CORTEXM_DHCSR_DBGKEY |
+		                                          CORTEXM_DHCSR_C_HALT |
+		                                          CORTEXM_DHCSR_C_DEBUGEN);
+	}
+	if (e.type) {
+		gdb_out("Timeout sending interrupt, is target in WFI?\n");
+	}
 }
 
 static int
@@ -480,10 +484,16 @@ cortexm_halt_wait(struct target_s *target)
 {
 	ADIv5_AP_t *ap = adiv5_target_ap(target);
 	struct cortexm_priv *priv = ap->priv;
-	if (!(target_mem_read32(target, CORTEXM_DHCSR) & CORTEXM_DHCSR_S_HALT))
-		return 0;
 
-	ap->dp->allow_timeout = false;
+	uint32_t dhcsr = 0;
+	volatile struct exception e;
+	TRY_CATCH (e, EXCEPTION_TIMEOUT) {
+		/* If this times out because the target is in WFI then
+		 * the target is still running. */
+		dhcsr = target_mem_read32(target, CORTEXM_DHCSR);
+	}
+	if (e.type || !(dhcsr & CORTEXM_DHCSR_S_HALT))
+		return 0;
 
 	/* We've halted.  Let's find out why. */
 	uint32_t dfsr = target_mem_read32(target, CORTEXM_DFSR);
@@ -543,7 +553,6 @@ void cortexm_halt_resume(struct target_s *target, bool step)
 	}
 
 	target_mem_write32(target, CORTEXM_DHCSR, dhcsr);
-	ap->dp->allow_timeout = true;
 }
 
 static int cortexm_fault_unwind(struct target_s *target)
diff --git a/src/include/adiv5.h b/src/include/adiv5.h
index 6896f6d..12d3bf4 100644
--- a/src/include/adiv5.h
+++ b/src/include/adiv5.h
@@ -107,12 +107,8 @@ typedef struct ADIv5_DP_s {
 
 	uint32_t idcode;
 
-	bool allow_timeout;
-
 	uint32_t (*dp_read)(struct ADIv5_DP_s *dp, uint16_t addr);
-
 	uint32_t (*error)(struct ADIv5_DP_s *dp);
-
 	uint32_t (*low_access)(struct ADIv5_DP_s *dp, uint8_t RnW,
                                uint16_t addr, uint32_t value);