diff --git a/Makefile b/Makefile
index 515cbb5..99c8660 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ AS := $(if $(AS)=as,$(CC),$(AS))
 LD := $(if $(LD)=ld,$(CC),$(LD))
 
 CFLAGS := $(if $(DEBUG),-O0 -g,-O3)
-CFLAGS += -std=c11 -Wall -Wextra
+CFLAGS += -std=c11 -Wall -Wextra -Wdouble-promotion
 
 
 #
diff --git a/src/spec.c b/src/spec.c
index a2c94f8..67cd4ac 100644
--- a/src/spec.c
+++ b/src/spec.c
@@ -646,12 +646,12 @@ static int estimate_noise(enum lc3_dt dt, enum lc3_bandwidth bw,
     for (i = 6*(3 + dt) - w; i < LC3_MIN(nq, bw_stop); i++) {
         z = xq[i] ? 0 : z + 1;
         if (z > 2*w)
-            sum += fabs(x[i - w]), n++;
+            sum += fabsf(x[i - w]), n++;
     }
 
     for ( ; i < bw_stop + w; i++)
         if (++z > 2*w)
-            sum += fabs(x[i - w]), n++;
+            sum += fabsf(x[i - w]), n++;
 
     int nf = n ? 8 - (int)((16 * sum) / n + 0.5f) : 0;