diff --git a/CHECKLST.txt b/CHECKLST.txt
index c3a5365a..82fc9d6a 100644
--- a/CHECKLST.txt
+++ b/CHECKLST.txt
@@ -37,6 +37,9 @@ Things to do during the branch-stabilisation period:
    particular, any headline features for the release should get a
    workout with memory checking enabled!
 
+ - Test the CMake build scripts with the oldest CMake they claim to
+   support, on both Unix and Windows.
+
 Making a release candidate build
 --------------------------------
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 299f04c4..16a0bc96 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.12)
+cmake_minimum_required(VERSION 3.7)
 project(putty LANGUAGES C)
 
 include(cmake/setup.cmake)
diff --git a/cmake/setup.cmake b/cmake/setup.cmake
index c0965c49..6612de97 100644
--- a/cmake/setup.cmake
+++ b/cmake/setup.cmake
@@ -55,9 +55,19 @@ add_custom_target(cmake_commit_c
   DEPENDS check_git_commit ${INTERMEDIATE_COMMIT_C}
   COMMENT "Updating cmake_commit.c")
 
+if(CMAKE_VERSION VERSION_LESS 3.12)
+  function(add_compile_definitions)
+    foreach(i ${ARGN})
+      add_compile_options(-D${i})
+    endforeach()
+  endfunction()
+endif()
+
 function(add_sources_from_current_dir target)
-  set(sources ${ARGN})
-  list(TRANSFORM sources PREPEND ${CMAKE_CURRENT_SOURCE_DIR}/)
+  set(sources)
+  foreach(i ${ARGN})
+    set(sources ${sources} ${CMAKE_CURRENT_SOURCE_DIR}/${i})
+  endforeach()
   target_sources(${target} PRIVATE ${sources})
 endfunction()
 
diff --git a/crypto/CMakeLists.txt b/crypto/CMakeLists.txt
index 7d11f444..c6420361 100644
--- a/crypto/CMakeLists.txt
+++ b/crypto/CMakeLists.txt
@@ -54,7 +54,9 @@ function(test_compile_with_flags outvar)
   endif()
 
   # See if we can compile the provided test program.
-  string(JOIN " " CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS} ${flags})
+  foreach(i ${flags})
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${i}")
+  endforeach()
   check_c_source_compiles("${OPT_TEST_SOURCE}" "${outvar}")
 
   if(${outvar} AND OPT_ADD_SOURCES_IF_SUCCESSFUL)
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index eb273758..cc90fcdc 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.12)
+cmake_minimum_required(VERSION 3.7)
 project(putty-documentation LANGUAGES)
 
 # This build script can be run standalone, or included as a
diff --git a/unix/CMakeLists.txt b/unix/CMakeLists.txt
index 37ea4337..a2332473 100644
--- a/unix/CMakeLists.txt
+++ b/unix/CMakeLists.txt
@@ -87,15 +87,15 @@ add_library(puttygen-common OBJECT
   ${CMAKE_SOURCE_DIR}/sshrand.c)
 
 add_executable(puttygen
-  ${CMAKE_SOURCE_DIR}/cmdgen.c)
-target_link_libraries(puttygen
-  puttygen-common keygen console crypto utils)
+  ${CMAKE_SOURCE_DIR}/cmdgen.c
+  $<TARGET_OBJECTS:puttygen-common>)
+target_link_libraries(puttygen keygen console crypto utils)
 installed_program(puttygen)
 
 add_executable(cgtest
-  ${CMAKE_SOURCE_DIR}/cgtest.c)
-target_link_libraries(cgtest
-  puttygen-common keygen console crypto utils)
+  ${CMAKE_SOURCE_DIR}/cgtest.c
+  $<TARGET_OBJECTS:puttygen-common>)
+target_link_libraries(cgtest keygen console crypto utils)
 
 add_executable(testsc
   ${CMAKE_SOURCE_DIR}/testsc.c)