diff --git a/libraries/AP_InternalError/AP_InternalError.cpp b/libraries/AP_InternalError/AP_InternalError.cpp
index c40d1029c2..d881f16de9 100644
--- a/libraries/AP_InternalError/AP_InternalError.cpp
+++ b/libraries/AP_InternalError/AP_InternalError.cpp
@@ -55,6 +55,7 @@ void AP_InternalError::errors_as_string(uint8_t *buffer, const uint16_t len) con
         "bad_rotation",
         "stack_ovrflw",  // stack_overflow
         "imu_reset",  // imu_reset
+        "gpio_isr",
     };
 
     static_assert((1U<<(ARRAY_SIZE(error_bit_descriptions))) == uint32_t(AP_InternalError::error_t::__LAST__), "too few descriptions for bits");
diff --git a/libraries/AP_InternalError/AP_InternalError.h b/libraries/AP_InternalError/AP_InternalError.h
index bd01cdf35d..9435039b67 100644
--- a/libraries/AP_InternalError/AP_InternalError.h
+++ b/libraries/AP_InternalError/AP_InternalError.h
@@ -62,7 +62,8 @@ public:
         bad_rotation                = (1U << 22),  //0x400000  4194304
         stack_overflow              = (1U << 23),  //0x800000  8388608
         imu_reset                   = (1U << 24),  //0x1000000 16777216
-        __LAST__                    = (1U << 25),  // used only for sanity check
+        gpio_isr                    = (1U << 25),  //0x2000000 33554432
+        __LAST__                    = (1U << 26),  // used only for sanity check
     };
 
     // if you've changed __LAST__ to be 32, then you will want to