diff --git a/celt/arch.h b/celt/arch.h
index dcfba763..6693408f 100644
--- a/celt/arch.h
+++ b/celt/arch.h
@@ -137,6 +137,22 @@ typedef float celt_sig;
 typedef float celt_norm;
 typedef float celt_ener;
 
+#ifdef FLOAT_APPROX
+/* This code should reliably detect NaN/inf even when -ffast-math is used.
+   Assumes IEEE 754 format. */
+static inline int celt_isnan(float x)
+{
+   union {float f; opus_uint32 i;} in;
+   in.f = x;
+   return ((in.i>>23)&0xFF)==0xFF && (in.i&0x007FFFFF)!=0;
+}
+#else
+#ifdef __FAST_MATH__
+#error Cannot build libopus with -ffast-math unless FLOAT_APPROX is defined. This could result in crashes on extreme (e.g. NaN) input
+#endif
+#define celt_isnan(x) ((x)!=(x))
+#endif
+
 #define Q15ONE 1.0f
 
 #define NORM_SCALING 1.f
diff --git a/src/mlp.c b/src/mlp.c
index 46386026..524e7711 100644
--- a/src/mlp.c
+++ b/src/mlp.c
@@ -75,6 +75,11 @@ static OPUS_INLINE float tansig_approx(float x)
         return 1;
     if (!(x>-8))
         return -1;
+#ifndef FIXED_POINT
+    /* Another check in case of -ffast-math */
+    if (celt_isnan(x))
+       return 0;
+#endif
 	if (x<0)
 	{
 	   x=-x;
diff --git a/src/mlp_data.c b/src/mlp_data.c
index 401c4c02..c2fda4e2 100644
--- a/src/mlp_data.c
+++ b/src/mlp_data.c
@@ -1,6 +1,10 @@
 /* The contents of this file was automatically generated by mlp_train.c
    It contains multi-layer perceptron (MLP) weights. */
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
 #include "mlp.h"
 
 /* RMS error was 0.138320, seed was 1361535663 */
diff --git a/src/opus_encoder.c b/src/opus_encoder.c
index c819bb15..411e3d24 100644
--- a/src/opus_encoder.c
+++ b/src/opus_encoder.c
@@ -1452,7 +1452,7 @@ opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_
        sum = celt_inner_prod(&pcm_buf[total_buffer*st->channels], &pcm_buf[total_buffer*st->channels], frame_size*st->channels);
        /* This should filter out both NaNs and ridiculous signals that could
           cause NaNs further down. */
-       if (!(sum < 1e9))
+       if (!(sum < 1e9) || celt_isnan(sum))
           OPUS_CLEAR(&pcm_buf[total_buffer*st->channels], frame_size*st->channels);
     }
 #endif