diff --git a/src/complex/ctanh.c b/src/complex/ctanh.c
index 0461050d73301adfad8e5571316d96b07556449a..3ba3a8997d80349099e4b9b98fcac27fae1f828d 100644
--- a/src/complex/ctanh.c
+++ b/src/complex/ctanh.c
@@ -101,11 +101,13 @@ double complex ctanh(double complex z)
 	}
 
 	/*
+	 * ctanh(+-0 + i NAN) = +-0 + i NaN
+	 * ctanh(+-0 +- i Inf) = +-0 + i NaN
 	 * ctanh(x + i NAN) = NaN + i NaN
 	 * ctanh(x +- i Inf) = NaN + i NaN
 	 */
 	if (!isfinite(y))
-		return CMPLX(y - y, y - y);
+		return CMPLX(x ? y - y : x, y - y);
 
 	/*
 	 * ctanh(+-huge + i +-y) ~= +-1 +- i 2sin(2y)/exp(2x), using the
diff --git a/src/complex/ctanhf.c b/src/complex/ctanhf.c
index a7e1a5fc0dccfdb8adeaf17b40794ebddf7c42a0..72b76da075cf83f26a3ea7297af2d0e5e052b039 100644
--- a/src/complex/ctanhf.c
+++ b/src/complex/ctanhf.c
@@ -50,7 +50,7 @@ float complex ctanhf(float complex z)
 	}
 
 	if (!isfinite(y))
-		return CMPLXF(y - y, y - y);
+		return CMPLXF(ix ? y - y : x, y - y);
 
 	if (ix >= 0x41300000) { /* x >= 11 */
 		float exp_mx = expf(-fabsf(x));