diff --git a/libraries/AC_PID/AC_PID.cpp b/libraries/AC_PID/AC_PID.cpp
index bd110b0009..2b3d5fec15 100644
--- a/libraries/AC_PID/AC_PID.cpp
+++ b/libraries/AC_PID/AC_PID.cpp
@@ -52,7 +52,7 @@ AC_PID::AC_PID(float initial_p, float initial_i, float initial_d, float initial_
     _kp = initial_p;
     _ki = initial_i;
     _kd = initial_d;
-    _imax = fabs(initial_imax);
+    _imax = fabsf(initial_imax);
     filt_hz(initial_filt_hz);
 
     // reset input filter to first value received
@@ -69,7 +69,7 @@ void AC_PID::set_dt(float dt)
 // filt_hz - set input filter hz
 void AC_PID::filt_hz(float hz)
 {
-    _filt_hz.set(fabs(hz));
+    _filt_hz.set(fabsf(hz));
 
     // sanity check _filt_hz
     _filt_hz = max(_filt_hz, AC_PID_FILT_HZ_MIN);
@@ -171,7 +171,7 @@ void AC_PID::load_gains()
     _ki.load();
     _kd.load();
     _imax.load();
-    _imax = fabs(_imax);
+    _imax = fabsf(_imax);
     _filt_hz.load();
 }
 
@@ -191,7 +191,7 @@ void AC_PID::operator() (float p, float i, float d, float imaxval, float input_f
     _kp = p;
     _ki = i;
     _kd = d;
-    _imax = fabs(imaxval);
+    _imax = fabsf(imaxval);
     _filt_hz = input_filt_hz;
     _dt = dt;
 }
diff --git a/libraries/AC_PID/AC_PID.h b/libraries/AC_PID/AC_PID.h
index 2fdec1d745..9f303841e3 100644
--- a/libraries/AC_PID/AC_PID.h
+++ b/libraries/AC_PID/AC_PID.h
@@ -69,7 +69,7 @@ public:
     void        kP(const float v) { _kp.set(v); }
     void        kI(const float v) { _ki.set(v); }
     void        kD(const float v) { _kd.set(v); }
-    void        imax(const float v) { _imax.set(fabs(v)); }
+    void        imax(const float v) { _imax.set(fabsf(v)); }
     void        filt_hz(const float v);
 
     float       get_integrator() const { return _integrator; }
diff --git a/libraries/AC_PID/AC_PI_2D.cpp b/libraries/AC_PID/AC_PI_2D.cpp
index deb216b46e..3c79ad38e4 100644
--- a/libraries/AC_PID/AC_PI_2D.cpp
+++ b/libraries/AC_PID/AC_PI_2D.cpp
@@ -40,7 +40,7 @@ AC_PI_2D::AC_PI_2D(float initial_p, float initial_i, float initial_imax, float i
 
     _kp = initial_p;
     _ki = initial_i;
-    _imax = fabs(initial_imax);
+    _imax = fabsf(initial_imax);
     filt_hz(initial_filt_hz);
 
     // reset input filter to first value received
@@ -58,7 +58,7 @@ void AC_PI_2D::set_dt(float dt)
 // filt_hz - set input filter hz
 void AC_PI_2D::filt_hz(float hz)
 {
-    _filt_hz.set(fabs(hz));
+    _filt_hz.set(fabsf(hz));
 
     // sanity check _filt_hz
     _filt_hz = max(_filt_hz, AC_PI_2D_FILT_HZ_MIN);
@@ -136,7 +136,7 @@ void AC_PI_2D::load_gains()
     _kp.load();
     _ki.load();
     _imax.load();
-    _imax = fabs(_imax);
+    _imax = fabsf(_imax);
     _filt_hz.load();
 
     // calculate the input filter alpha
@@ -157,7 +157,7 @@ void AC_PI_2D::operator() (float p, float i, float imaxval, float input_filt_hz,
 {
     _kp = p;
     _ki = i;
-    _imax = fabs(imaxval);
+    _imax = fabsf(imaxval);
     _filt_hz = input_filt_hz;
     _dt = dt;
     // calculate the input filter alpha
diff --git a/libraries/AC_PID/AC_PI_2D.h b/libraries/AC_PID/AC_PI_2D.h
index d6a27caa43..30a6d1f79d 100644
--- a/libraries/AC_PID/AC_PI_2D.h
+++ b/libraries/AC_PID/AC_PI_2D.h
@@ -62,7 +62,7 @@ public:
     // set accessors
     void        kP(const float v) { _kp.set(v); }
     void        kI(const float v) { _ki.set(v); }
-    void        imax(const float v) { _imax.set(fabs(v)); }
+    void        imax(const float v) { _imax.set(fabsf(v)); }
     void        filt_hz(const float v);
 
     Vector2f    get_integrator() const { return _integrator; }