diff --git a/libraries/AP_Math/AP_Math.cpp b/libraries/AP_Math/AP_Math.cpp
index 4476aec439..1b17bbf304 100644
--- a/libraries/AP_Math/AP_Math.cpp
+++ b/libraries/AP_Math/AP_Math.cpp
@@ -211,3 +211,11 @@ uint16_t get_random16(void)
     return ((m_z << 16) + m_w) & 0xFFFF;
 }
 
+
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+// generate a random float between -1 and 1, for use in SITL
+float rand_float(void)
+{
+    return ((((unsigned)random()) % 2000000) - 1.0e6) / 1.0e6;
+}
+#endif
diff --git a/libraries/AP_Math/AP_Math.h b/libraries/AP_Math/AP_Math.h
index 2969e10577..b3ad2ad106 100644
--- a/libraries/AP_Math/AP_Math.h
+++ b/libraries/AP_Math/AP_Math.h
@@ -221,3 +221,6 @@ float linear_interpolate(float low_output, float high_output,
 /* simple 16 bit random number generator */
 uint16_t get_random16(void);
 
+// generate a random float between -1 and 1, for use in SITL
+float rand_float(void);
+