diff --git a/libraries/AP_Math/matrix3.h b/libraries/AP_Math/matrix3.h
index f6494b56b9..e19bf2a158 100644
--- a/libraries/AP_Math/matrix3.h
+++ b/libraries/AP_Math/matrix3.h
@@ -128,7 +128,7 @@ public:
     // allow a Matrix3 to be used as an array of vectors, 0 indexed
     Vector3<T> & operator[](uint8_t i) {
         Vector3<T> *_v = &a;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < 3);
 #endif
         return _v[i];
@@ -136,7 +136,7 @@ public:
 
     const Vector3<T> & operator[](uint8_t i) const {
         const Vector3<T> *_v = &a;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < 3);
 #endif
         return _v[i];
diff --git a/libraries/AP_Math/quaternion.h b/libraries/AP_Math/quaternion.h
index faa0361b46..2786149a00 100644
--- a/libraries/AP_Math/quaternion.h
+++ b/libraries/AP_Math/quaternion.h
@@ -21,7 +21,7 @@
 #define QUATERNION_H
 
 #include <math.h>
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
 #include <assert.h>
 #endif
 
@@ -90,7 +90,7 @@ public:
     // allow a quaternion to be used as an array, 0 indexed
     float & operator[](uint8_t i) {
         float *_v = &q1;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i < 4);
 #endif
         return _v[i];
@@ -98,7 +98,7 @@ public:
 
     const float & operator[](uint8_t i) const {
         const float *_v = &q1;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i < 4);
 #endif
         return _v[i];
diff --git a/libraries/AP_Math/vector3.h b/libraries/AP_Math/vector3.h
index c7cc7b36da..cafa60adff 100644
--- a/libraries/AP_Math/vector3.h
+++ b/libraries/AP_Math/vector3.h
@@ -53,7 +53,7 @@
 #include <math.h>
 #include <string.h>
 
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
 #include <assert.h>
 #endif
 
@@ -118,7 +118,7 @@ public:
     // allow a vector3 to be used as an array, 0 indexed
     T & operator[](uint8_t i) {
         T *_v = &x;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < 3);
 #endif
         return _v[i];
@@ -126,7 +126,7 @@ public:
 
     const T & operator[](uint8_t i) const {
         const T *_v = &x;
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < 3);
 #endif
         return _v[i];
diff --git a/libraries/AP_Math/vectorN.h b/libraries/AP_Math/vectorN.h
index cfd4bb4def..9bd051446c 100644
--- a/libraries/AP_Math/vectorN.h
+++ b/libraries/AP_Math/vectorN.h
@@ -19,7 +19,7 @@
 
 #include <math.h>
 #include <string.h>
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
 #include <assert.h>
 #endif
 
@@ -33,14 +33,14 @@ public:
     }
 
     inline T & operator[](uint8_t i) {
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < N);
 #endif
         return _v[i];
     }
 
     inline const T & operator[](uint8_t i) const {
-#if MATH_CHECK_INDEXES
+#if defined(MATH_CHECK_INDEXES) && (MATH_CHECK_INDEXES == 1)
         assert(i >= 0 && i < N);
 #endif
         return _v[i];