diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 3ece82c4d..04c47019e 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -98,7 +98,7 @@ class Dependency:
 
     def __init__(self, type_name, kwargs):
         self.name = "null"
-        self.version = 'none'
+        self.version = None
         self.language = None # None means C-like
         self.is_found = False
         self.type_name = type_name
@@ -138,7 +138,10 @@ class Dependency:
         return self.name
 
     def get_version(self):
-        return self.version
+        if self.version:
+            return self.version
+        else:
+            return 'unknown'
 
     def get_exe_args(self, compiler):
         return []
@@ -283,22 +286,34 @@ class ExternalDependency(Dependency):
             return
 
         if self.version_reqs:
-            (self.is_found, not_found, found) = \
-                version_compare_many(self.version, self.version_reqs)
-            if not self.is_found:
+            # an unknown version can never satisfy any requirement
+            if not self.version:
                 found_msg = ['Dependency', mlog.bold(self.name), 'found:']
-                found_msg += [mlog.red('NO'),
-                              'found {!r} but need:'.format(self.version),
-                              ', '.join(["'{}'".format(e) for e in not_found])]
-                if found:
-                    found_msg += ['; matched:',
-                                  ', '.join(["'{}'".format(e) for e in found])]
+                found_msg += [mlog.red('NO'), 'unknown version, but need:',
+                              self.version_reqs]
                 mlog.log(*found_msg)
 
                 if self.required:
-                    m = 'Invalid version of dependency, need {!r} {!r} found {!r}.'
-                    raise DependencyException(m.format(self.name, not_found, self.version))
-                return
+                    m = 'Unknown version of dependency {!r}, but need {!r}.'
+                    raise DependencyException(m.format(self.name, self.version_reqs))
+
+            else:
+                (self.is_found, not_found, found) = \
+                    version_compare_many(self.version, self.version_reqs)
+                if not self.is_found:
+                    found_msg = ['Dependency', mlog.bold(self.name), 'found:']
+                    found_msg += [mlog.red('NO'),
+                                  'found {!r} but need:'.format(self.version),
+                                  ', '.join(["'{}'".format(e) for e in not_found])]
+                    if found:
+                        found_msg += ['; matched:',
+                                      ', '.join(["'{}'".format(e) for e in found])]
+                    mlog.log(*found_msg)
+
+                    if self.required:
+                        m = 'Invalid version of dependency, need {!r} {!r} found {!r}.'
+                        raise DependencyException(m.format(self.name, not_found, self.version))
+                    return
 
 
 class NotFoundDependency(Dependency):
@@ -400,7 +415,7 @@ class ConfigToolDependency(ExternalDependency):
             # don't fail with --version, in that case just assume that there is
             # only one version and return it.
             if not out:
-                return (tool, 'none')
+                return (tool, None)
             if versions:
                 is_found = version_compare_many(out, versions)[0]
                 # This allows returning a found version without a config tool,
@@ -1236,9 +1251,6 @@ class ExtraFrameworkDependency(ExternalDependency):
                 self.is_found = True
                 return
 
-    def get_version(self):
-        return 'unknown'
-
     def log_info(self):
         return os.path.join(self.path, self.name)
 
@@ -1331,7 +1343,7 @@ def find_external_dependency(name, env, kwargs):
                 if info:
                     info = ', ' + info
 
-                mlog.log(type_text, mlog.bold(display_name), details + 'found:', mlog.green('YES'), d.version + info)
+                mlog.log(type_text, mlog.bold(display_name), details + 'found:', mlog.green('YES'), (d.version if d.version else '') + info)
 
                 return d
 
diff --git a/mesonbuild/dependencies/dev.py b/mesonbuild/dependencies/dev.py
index 0cd3c2bcb..087639107 100644
--- a/mesonbuild/dependencies/dev.py
+++ b/mesonbuild/dependencies/dev.py
@@ -35,7 +35,6 @@ class GTestDependency(ExternalDependency):
         self.detect()
 
     def detect(self):
-        self.version = '1.something_maybe'
         gtest_detect = self.clib_compiler.find_library("gtest", self.env, [])
         gtest_main_detect = self.clib_compiler.find_library("gtest_main", self.env, [])
         if gtest_detect and (not self.main or gtest_main_detect):
@@ -85,7 +84,6 @@ class GTestDependency(ExternalDependency):
 class GMockDependency(ExternalDependency):
     def __init__(self, environment, kwargs):
         super().__init__('gmock', environment, 'cpp', kwargs)
-        self.version = '1.something_maybe'
         # GMock may be a library or just source.
         # Work with both.
         gmock_detect = self.clib_compiler.find_library("gmock", self.env, [])
diff --git a/mesonbuild/dependencies/misc.py b/mesonbuild/dependencies/misc.py
index 72bda521d..014be84ab 100644
--- a/mesonbuild/dependencies/misc.py
+++ b/mesonbuild/dependencies/misc.py
@@ -180,7 +180,7 @@ class MPIDependency(ExternalDependency):
             if version:
                 version = version.group(0)
             else:
-                version = 'none'
+                version = None
 
             return version, cargs, libs
 
@@ -197,7 +197,7 @@ class MPIDependency(ExternalDependency):
                 return
             args = shlex.split(o)
 
-            version = 'none'
+            version = None
 
             return version, args, args
 
@@ -222,11 +222,11 @@ class MPIDependency(ExternalDependency):
         else:
             return
         if self.language == 'fortran':
-            return ('none',
+            return (None,
                     ['-I' + incdir, '-I' + os.path.join(incdir, post)],
                     [os.path.join(libdir, 'msmpi.lib'), os.path.join(libdir, 'msmpifec.lib')])
         else:
-            return ('none',
+            return (None,
                     ['-I' + incdir, '-I' + os.path.join(incdir, post)],
                     [os.path.join(libdir, 'msmpi.lib')])
 
@@ -274,9 +274,6 @@ class ThreadDependency(ExternalDependency):
     def need_threads(self):
         return True
 
-    def get_version(self):
-        return 'unknown'
-
 
 class Python3Dependency(ExternalDependency):
     def __init__(self, environment, kwargs):
diff --git a/mesonbuild/dependencies/platform.py b/mesonbuild/dependencies/platform.py
index e17a2f2d0..0c051563d 100644
--- a/mesonbuild/dependencies/platform.py
+++ b/mesonbuild/dependencies/platform.py
@@ -34,6 +34,3 @@ class AppleFrameworks(ExternalDependency):
             self.link_args += ['-framework', f]
 
         self.is_found = mesonlib.is_osx()
-
-    def get_version(self):
-        return 'unknown'
diff --git a/mesonbuild/dependencies/ui.py b/mesonbuild/dependencies/ui.py
index 34c9fb28f..f19a76d32 100644
--- a/mesonbuild/dependencies/ui.py
+++ b/mesonbuild/dependencies/ui.py
@@ -44,14 +44,12 @@ class GLDependency(ExternalDependency):
             # FIXME: Use AppleFrameworks dependency
             self.link_args = ['-framework', 'OpenGL']
             # FIXME: Detect version using self.clib_compiler
-            self.version = '1'
             return
         if mesonlib.is_windows():
             self.is_found = True
             # FIXME: Use self.clib_compiler.find_library()
             self.link_args = ['-lopengl32']
             # FIXME: Detect version using self.clib_compiler
-            self.version = '1'
             return
 
     @classmethod
@@ -224,7 +222,7 @@ class QtBaseDependency(ExternalDependency):
             self.compile_args = []
             self.link_args = []
             self.from_text = mlog.format_list(methods)
-            self.version = 'none'
+            self.version = None
 
     def compilers_detect(self):
         "Detect Qt (4 or 5) moc, uic, rcc in the specified bindir or in PATH"
@@ -557,7 +555,6 @@ class VulkanDependency(ExternalDependency):
 
             # TODO: find a way to retrieve the version from the sdk?
             # Usually it is a part of the path to it (but does not have to be)
-            self.version = '1'
             return
         else:
             # simply try to guess it, usually works on linux
@@ -565,7 +562,6 @@ class VulkanDependency(ExternalDependency):
             if libs is not None and self.clib_compiler.has_header('vulkan/vulkan.h', '', environment):
                 self.type_name = 'system'
                 self.is_found = True
-                self.version = 1 # TODO
                 for lib in libs:
                     self.link_args.append(lib)
                 return