diff --git a/CMakeLists.txt b/CMakeLists.txt
index 97447ce01..988c12cff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -126,7 +126,6 @@ set(LIBAPPINDICATOR_MINIMUM 0.4.90)
 set(OPENSSL_MINIMUM         0.9.7)
 set(POLARSSL_MINIMUM        1.2)
 set(QT_MINIMUM              5.6)
-set(ZLIB_MINIMUM            1.2.3)
 
 if(WIN32)
     foreach(L C CXX)
@@ -325,11 +324,6 @@ if(ENABLE_MAC)
     tr_fixup_auto_option(ENABLE_MAC MAC_FOUND MAC_IS_REQUIRED)
 endif()
 
-find_package(ZLIB ${ZLIB_MINIMUM})
-if(ZLIB_FOUND)
-    add_definitions(-DHAVE_ZLIB)
-endif()
-
 set(THIRD_PARTY_DIR ${CMAKE_SOURCE_DIR}/third-party)
 
 tr_add_external_auto_library(DEFLATE libdeflate deflate)
diff --git a/Transmission.xcodeproj/project.pbxproj b/Transmission.xcodeproj/project.pbxproj
index 710f4f758..1550525b4 100644
--- a/Transmission.xcodeproj/project.pbxproj
+++ b/Transmission.xcodeproj/project.pbxproj
@@ -3616,9 +3616,6 @@
 					"-D__TRANSMISSION__",
 					"-DHAVE_FLOCK",
 					"-DHAVE_STRLCPY",
-					"-DHAVE_ASPRINTF",
-					"-DHAVE_LIBGEN",
-					"-DHAVE_ZLIB",
 					"-DHAVE_ICONV",
 				);
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
@@ -3831,9 +3828,6 @@
 					"-D__TRANSMISSION__",
 					"-DHAVE_FLOCK",
 					"-DHAVE_STRLCPY",
-					"-DHAVE_ASPRINTF",
-					"-DHAVE_LIBGEN",
-					"-DHAVE_ZLIB",
 					"-DHAVE_ICONV",
 				);
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
@@ -4118,9 +4112,6 @@
 					"-D__TRANSMISSION__",
 					"-DHAVE_FLOCK",
 					"-DHAVE_STRLCPY",
-					"-DHAVE_ASPRINTF",
-					"-DHAVE_LIBGEN",
-					"-DHAVE_ZLIB",
 					"-DHAVE_ICONV",
 				);
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";