diff --git a/ANNOUNCE b/ANNOUNCE
index 8ce75e580eb9f27ee87339acdeddd097fdf46846..0e3a902bb34695e0412004e80316b2515db7a794 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.31beta01 - July 1, 2017
+Libpng 1.6.31beta01 - July 3, 2017
 
 This is not intended to be a public release. It will be replaced
 within a few weeks by a public version or by another test version.
@@ -60,11 +60,13 @@ Version 1.6.30rc02 [June 25, 2017]
 Version 1.6.30 [June 28, 2017]
   No changes.
 
-Version 1.6.31beta01 [July 1, 2017]
+Version 1.6.31beta01 [July 3, 2017]
   Guard the definition of _POSIX_SOURCE in pngpriv.h (AIX already defines it;
     bug report by Michael Felt).
   Revised pngpriv.h to work around failure to compile arm/filter_neon.S
-    ("typedef" directive is unrecognized by the assembler).
+    ("typedef" directive is unrecognized by the assembler). The problem
+    was introduced in libpng-1.6.30beta01.
+  Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 26302965db883062b7468d5edce49c5c89bae071..7370895d34e9813d01580d8eb1f34191cc34a869 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5855,11 +5855,13 @@ Version 1.6.30rc02 [June 25, 2017]
 Version 1.6.30 [June 28, 2017]
   No changes.
 
-Version 1.6.31beta01 [July 1, 2017]
+Version 1.6.31beta01 [July 3, 2017]
   Guard the definition of _POSIX_SOURCE in pngpriv.h (AIX already defines it;
     bug report by Michael Felt).
   Revised pngpriv.h to work around failure to compile arm/filter_neon.S
-    ("typedef" directive is unrecognized by the assembler).
+    ("typedef" directive is unrecognized by the assembler). The problem
+    was introduced in libpng-1.6.30beta01.
+  Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/libpng.pc.in b/libpng.pc.in
index 3e7e2c58a7effd223f31153e65a9b92d59bc54f7..9708e9af2be1259147c6244c07345f39222cbea4 100644
--- a/libpng.pc.in
+++ b/libpng.pc.in
@@ -6,6 +6,7 @@ includedir=@includedir@/libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@
 Name: libpng
 Description: Loads and saves PNG files
 Version: @PNGLIB_VERSION@
+Requires: zlib
 Libs: -L${libdir} -lpng@PNGLIB_MAJOR@@PNGLIB_MINOR@
 Libs.private: @LIBS@
 Cflags: -I${includedir}