diff --git a/.ci/ci-script.sh b/.ci/ci-script.sh
index 1c31e25f1..f19c9f50c 100755
--- a/.ci/ci-script.sh
+++ b/.ci/ci-script.sh
@@ -51,7 +51,7 @@ fi
 
 target_configure()
 {
-  cmake -DTEMPORAIRLY_ALLOW_OLD_TOOCHAIN=ON -DCMAKE_INSTALL_PREFIX="$INSTALL_PREFIX" -G"$GENERATOR" -DCMAKE_BUILD_TYPE="$CMAKE_BUILD_TYPE" $ECO "$SRC_DIR" || (cat "$BUILD_DIR"/CMakeFiles/CMakeOutput.log; cat "$BUILD_DIR"/CMakeFiles/CMakeError.log)
+  cmake -DCMAKE_INSTALL_PREFIX="$INSTALL_PREFIX" -G"$GENERATOR" -DCMAKE_BUILD_TYPE="$CMAKE_BUILD_TYPE" $ECO "$SRC_DIR" || (cat "$BUILD_DIR"/CMakeFiles/CMakeOutput.log; cat "$BUILD_DIR"/CMakeFiles/CMakeError.log)
 }
 
 target_build()
diff --git a/.ci/oss-fuzz.sh b/.ci/oss-fuzz.sh
index a337a2dcc..93d0a8e75 100755
--- a/.ci/oss-fuzz.sh
+++ b/.ci/oss-fuzz.sh
@@ -64,7 +64,7 @@ cmake \
   -DCMAKE_BUILD_TYPE=FUZZ -DBUILD_FUZZERS=ON \
   -DLIB_FUZZING_ENGINE:STRING="$LIB_FUZZING_ENGINE" \
   -DCMAKE_INSTALL_PREFIX:PATH="$OUT" -DCMAKE_INSTALL_BINDIR:PATH="$OUT" \
-  -DTEMPORAIRLY_ALLOW_OLD_TOOCHAIN=ON "$SRC/librawspeed/"
+  "$SRC/librawspeed/"
 
 cmake --build . -- -j$(nproc) all && cmake --build . -- -j$(nproc) install
 
diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 61702545f..60177d703 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -56,7 +56,6 @@ jobs:
           - { distro: "debian:bookworm-slim", family: GNU,  version: 12, CC: gcc-12,   CXX: g++-12 }
           - { distro: "debian:trixie-slim",   family: LLVM, version: 17, CC: clang-17, CXX: clang++-17 }
           - { distro: "debian:bookworm-slim", family: LLVM, version: 16, CC: clang-16, CXX: clang++-16 }
-          - { distro: "debian:bookworm-slim", family: LLVM, version: 15, CC: clang-15, CXX: clang++-15 }
         flavor: [ ReleaseWithAsserts, Release ]
     uses: ./.github/workflows/CI-linux.yml
     with:
diff --git a/cmake/compiler-versions.cmake b/cmake/compiler-versions.cmake
index d838afa40..50eb049f7 100644
--- a/cmake/compiler-versions.cmake
+++ b/cmake/compiler-versions.cmake
@@ -26,10 +26,9 @@
 #   coming with gcc-14 and LLVM18
 # * macOS 13 (Ventura) be the oldest supported macOS version,
 #   with the newest supported Xcode version being 15.2 (LLVM16-based !)
-# * (as of 2024-02-14) oss-fuzz provides LLVM15.
+# * (as of 2024-04-30) oss-fuzz provides LLVM18~.
 #
-# Therefore, we currently require GCC12, macOS 13.5 + Xcode 15.2, and LLVM15,
-# and, pending oss-fuzz roll-forward, LLVM16.
+# Therefore, we currently require GCC12, macOS 13.5 + Xcode 15.2, and LLVM16.
 
 if(CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 12)
   message(SEND_ERROR "GNU C compiler version ${CMAKE_C_COMPILER_VERSION} is too old and is unsupported. Version 12+ is required.")
@@ -38,24 +37,11 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_L
   message(SEND_ERROR "GNU C++ compiler version ${CMAKE_CXX_COMPILER_VERSION} is too old and is unsupported. Version 12+ is required.")
 endif()
 
-if(NOT TEMPORAIRLY_ALLOW_OLD_TOOCHAIN)
-  if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 16)
-    set(FAILURE ON)
-  endif()
-  if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16)
-    set(FAILURE ON)
-  endif()
-  if(FAILURE)
-    message(SEND_ERROR "LLVM Clang compiler version ${CMAKE_C_COMPILER_VERSION} is too old and is about to become unsupported. Version 16+ is to be required.")
-    message(SEND_ERROR "If you are seeing this message, please complain before March 4'th on https://github.com/darktable-org/darktable/pull/16374 and this will be temporarily reverted (but will be reinstated after Ubuntu 24.04 has been released, on April 25'th)")
-  endif()
-else()
-  if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 15)
-    message(SEND_ERROR "LLVM Clang C compiler version ${CMAKE_C_COMPILER_VERSION} is too old and is unsupported. Version 15+ is required.")
-  endif()
-  if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 15)
-    message(SEND_ERROR "LLVM Clang C++ compiler version ${CMAKE_CXX_COMPILER_VERSION} is too old and is unsupported. Version 15+ is required.")
-  endif()
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION VERSION_LESS 16)
+  message(SEND_ERROR "LLVM Clang C compiler version ${CMAKE_C_COMPILER_VERSION} is too old and is unsupported. Version 16+ is required.")
+endif()
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 16)
+  message(SEND_ERROR "LLVM Clang C++ compiler version ${CMAKE_CXX_COMPILER_VERSION} is too old and is unsupported. Version 16+ is required.")
 endif()
 
 # XCode 15.2 (apple clang 15.0.0.15000100) is based on LLVM16
@@ -102,8 +88,6 @@ if(NOT DEFINED RAWSPEED_LIBCXX_MIN)
   if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
     set(LIBCXX_MIN 160000)
   else()
-    # Yes, even though we support using clang-15 (because of oss-fuzz),
-    # if you are using libc++, we require libc++-16.
     set(LIBCXX_MIN 16000)
   endif()
   message(STATUS "Performing libc++ version check")