diff --git a/repo2docker/buildpacks/julia/julia_project.py b/repo2docker/buildpacks/julia/julia_project.py
index 0d039aae7..0e9f9daa4 100644
--- a/repo2docker/buildpacks/julia/julia_project.py
+++ b/repo2docker/buildpacks/julia/julia_project.py
@@ -1,8 +1,10 @@
 """Generates a Dockerfile based on an input matrix for Julia"""
+import functools
 import os
+import requests
 import toml
 from ..python import PythonBuildPack
-from .semver import find_semver_match
+from .semver import find_semver_match, semver
 
 
 class JuliaProjectTomlBuildPack(PythonBuildPack):
@@ -13,48 +15,44 @@ class JuliaProjectTomlBuildPack(PythonBuildPack):
     # ALL EXISTING JULIA VERSIONS
     # Note that these must remain ordered, in order for the find_semver_match()
     # function to behave correctly.
-    all_julias = [
-        "0.7.0",
-        "1.0.0",
-        "1.0.1",
-        "1.0.2",
-        "1.0.3",
-        "1.0.4",
-        "1.0.5",
-        "1.1.0",
-        "1.1.1",
-        "1.2.0",
-        "1.3.0",
-        "1.3.1",
-        "1.4.0",
-        "1.4.1",
-        "1.4.2",
-        "1.5.0",
-        "1.5.1",
-        "1.5.2",
-        "1.5.3",
-    ]
+    @property
+    @functools.lru_cache(maxsize=1)
+    def all_julias(self):
+        try:
+            json = requests.get(
+                "https://julialang-s3.julialang.org/bin/versions.json"
+            ).json()
+        except Exception as e:
+            raise RuntimeError("Failed to fetch available Julia versions: {e}")
+        vers = [semver.VersionInfo.parse(v) for v in json.keys()]
+        # filter out pre-release versions not supported by find_semver_match()
+        filtered_vers = [v for v in vers if v.prerelease is None]
+        # properly sort list of VersionInfo
+        sorted_vers = sorted(
+            filtered_vers, key=functools.cmp_to_key(semver.VersionInfo.compare)
+        )
+        # return list of semver string
+        return [str(v) for v in sorted_vers]
 
     @property
     def julia_version(self):
-        default_julia_version = self.all_julias[-1]
-
         if os.path.exists(self.binder_path("JuliaProject.toml")):
             project_toml = toml.load(self.binder_path("JuliaProject.toml"))
         else:
             project_toml = toml.load(self.binder_path("Project.toml"))
 
-        if "compat" in project_toml:
-            if "julia" in project_toml["compat"]:
-                julia_version_str = project_toml["compat"]["julia"]
-
-                # For Project.toml files, install the latest julia version that
-                # satisfies the given semver.
-                _julia_version = find_semver_match(julia_version_str, self.all_julias)
-                if _julia_version is not None:
-                    return _julia_version
-
-        return default_julia_version
+        try:
+            # For Project.toml files, install the latest julia version that
+            # satisfies the given semver.
+            compat = project_toml["compat"]["julia"]
+        except:
+            # Default version which needs to be manually updated with new major.minor releases
+            compat = "1.5"
+
+        match = find_semver_match(compat, self.all_julias)
+        if match is None:
+            raise RuntimeError("Failed to find a matching Julia version: {compat}")
+        return match
 
     def get_build_env(self):
         """Get additional environment settings for Julia and Jupyter
diff --git a/repo2docker/buildpacks/julia/semver.py b/repo2docker/buildpacks/julia/semver.py
index accd31922..da9bf7c77 100644
--- a/repo2docker/buildpacks/julia/semver.py
+++ b/repo2docker/buildpacks/julia/semver.py
@@ -113,7 +113,8 @@ def match(self, v):
         while len(v) < 3:
             v = v + (0,)
         v_str = ".".join(map(str, v))
-        return semver.match(v_str, self.constraint_str)
+        v_ver = semver.VersionInfo.parse(v_str)
+        return semver.VersionInfo.match(v_ver, self.constraint_str)
 
     def __eq__(self, rhs):
         return self.constraint_str == rhs.constraint_str