diff --git a/ci/build-in-docker.sh b/ci/build-in-docker.sh
index 5ee5ee9..42e4283 100755
--- a/ci/build-in-docker.sh
+++ b/ci/build-in-docker.sh
@@ -31,8 +31,7 @@ case "$ARCH" in
 esac
 
 # libassuan-static is supported only from 3.19 onwards
-# TODO: change this to a stable release once Alpine 3.19 was released
-image="$image_prefix"/alpine:edge
+image="$image_prefix"/alpine:3.19
 
 repo_root="$(readlink -f "$(dirname "${BASH_SOURCE[0]}")"/..)"
 
diff --git a/src/appimagetool.c b/src/appimagetool.c
index 6c22fbd..1233c9a 100644
--- a/src/appimagetool.c
+++ b/src/appimagetool.c
@@ -877,8 +877,8 @@ main (int argc, char *argv[])
         } else {
             if (!fetch_runtime(arch, &size, &data, verbose)) {
                 die(
-                    "Failed to download runtime file, please download the runtime manually from"
-                    "https://github.com/AppImage/type2-runtime/releases and pass it to appimagetool with"
+                    "Failed to download runtime file, please download the runtime manually from "
+                    "https://github.com/AppImage/type2-runtime/releases and pass it to appimagetool with "
                     "--runtime-file"
                 );
             }
diff --git a/src/appimagetool_fetch_runtime.cpp b/src/appimagetool_fetch_runtime.cpp
index 5c7c225..be996a1 100644
--- a/src/appimagetool_fetch_runtime.cpp
+++ b/src/appimagetool_fetch_runtime.cpp
@@ -134,57 +134,72 @@ class GetRequest {
     }
 
     void setUpTlsCaChainCompatibility(bool verbose) {
+        bool foundFile = false;
+        bool foundDir = false;
+
         // from curl 7.84.0 on, one can query the default values and check if these files or directories exist
         // if not, we anyway run the detection
 #define querying_supported LIBCURL_VERSION_NUM >= CURL_VERSION_BITS(7, 84, 0)
 #if querying_supported
         {
             const auto caInfo = getOption<char*>(CURLINFO_CAINFO);
-            if (std::filesystem::exists(caInfo)) {
+            if (caInfo != nullptr && std::filesystem::exists(caInfo)) {
                 if (verbose) {
                     std::cerr << "libcurl's default CA certificate bundle file " << caInfo << " was found on this system" << std::endl;
                 }
-                return;
+                foundFile = true;
+            } else {
+                if (verbose) {
+                    std::cerr << "libcurl's default CA certificate bundle file " << caInfo << " was not found on this system, nulling" << std::endl;
+                }
+                setOption(CURLOPT_CAINFO, "");
             }
         }
 
         {
             const auto caPath = getOption<char*>(CURLINFO_CAPATH);
-            if (std::filesystem::is_directory(caPath)) {
+            if (caPath != nullptr && std::filesystem::is_directory(caPath)) {
                 if (verbose) {
                     std::cerr << "libcurl's default CA certificate bundle directory " << caPath
                               << " was found on this system" << std::endl;
                 }
-                return;
+                foundDir = true;
+            } else {
+                if (verbose) {
+                    std::cerr << "libcurl's default CA certificate bundle directory " << caPath << " was not found on this system, nulling" << std::endl;
+                }
+                setOption(CURLOPT_CAPATH, "");
             }
         }
 #else
 #warning "libcurl version too old, not trying to use default values for system-provided CA certificate bundles"
 #endif
 
-        {
+        if (!foundFile) {
             const auto chainFile = findCaBundleFile();
             if (!chainFile.empty()) {
                 if (verbose) {
                     std::cerr << "Using CA bundle file in " << chainFile << std::endl;
                 }
                 setOption(CURLOPT_CAINFO, chainFile.c_str());
-                return;
             }
+            foundFile = true;
         }
 
-        {
+        if (!foundDir) {
             const auto chainDir = findCaBundleDirectory();
             if (!chainDir.empty()) {
                 if (verbose) {
-                    std::cerr << "Using CA bundle file in " << chainDir << std::endl;
+                    std::cerr << "Using CA bundle dir in " << chainDir << std::endl;
                 }
-                setOption(CURLOPT_CAINFO, chainDir.c_str());
-                return;
+                setOption(CURLOPT_CAPATH, chainDir.c_str());
             }
+            foundDir = true;
         }
 
-        std::cerr << "Warning: could not find valid CA chain bundle, HTTPS requests will likely fail" << std::endl;
+        if (!foundFile && !foundDir) {
+            std::cerr << "Warning: could not find valid CA chain bundle, HTTPS requests will likely fail" << std::endl;
+        }
     }
 
 public: