diff --git a/app/src/main/java/eu/faircode/email/ConnectionHelper.java b/app/src/main/java/eu/faircode/email/ConnectionHelper.java
index e4c16c0dbd..02cc930afd 100644
--- a/app/src/main/java/eu/faircode/email/ConnectionHelper.java
+++ b/app/src/main/java/eu/faircode/email/ConnectionHelper.java
@@ -533,6 +533,9 @@ public class ConnectionHelper {
     }
 
     static boolean isNumericAddress(String host) {
+        // IPv4-mapped IPv6 can be 45 characters
+        if (host == null || host.length() > 64)
+            return false;
         return ConnectionHelper.jni_is_numeric_address(host);
     }
 
diff --git a/app/src/main/jni/fairemail.cc b/app/src/main/jni/fairemail.cc
index 46377d8c26..9af3ec9d26 100644
--- a/app/src/main/jni/fairemail.cc
+++ b/app/src/main/jni/fairemail.cc
@@ -13,7 +13,7 @@
 
 void log_android(int prio, const char *fmt, ...) {
     if (prio >= ANDROID_LOG_DEBUG) {
-        char line[4096];
+        char line[1024];
         va_list argptr;
         va_start(argptr, fmt);
         vsprintf(line, fmt, argptr);