diff --git a/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/floris/TextKeyData.kt b/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/floris/TextKeyData.kt
index c5ec0ad6..dc527ce5 100644
--- a/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/floris/TextKeyData.kt
+++ b/app/src/main/java/helium314/keyboard/keyboard/internal/keyboard_parser/floris/TextKeyData.kt
@@ -337,7 +337,7 @@ sealed interface KeyData : AbstractKeyData {
     }
 
     override fun compute(params: KeyboardParams): KeyData? {
-        require(groupId <= GROUP_ENTER) { "only groups up to GROUP_ENTER are supported" }
+        require(groupId in 0..GROUP_ENTER) { "only positive groupIds up to GROUP_ENTER are supported" }
         require(label.isNotEmpty() || type == KeyType.PLACEHOLDER || code != KeyCode.UNSPECIFIED) { "non-placeholder key has no code and no label" }
         require(width >= 0f || width == -1f) { "illegal width $width" }
         val newLabel = label.convertFlorisLabel().resolveStringLabel(params)
diff --git a/app/src/main/java/helium314/keyboard/latin/utils/CustomLayoutUtils.kt b/app/src/main/java/helium314/keyboard/latin/utils/CustomLayoutUtils.kt
index e5ce2773..c314865d 100644
--- a/app/src/main/java/helium314/keyboard/latin/utils/CustomLayoutUtils.kt
+++ b/app/src/main/java/helium314/keyboard/latin/utils/CustomLayoutUtils.kt
@@ -20,6 +20,7 @@ import helium314.keyboard.keyboard.internal.keyboard_parser.addLocaleKeyTextsToP
 import helium314.keyboard.latin.R
 import helium314.keyboard.latin.common.Constants
 import helium314.keyboard.latin.common.FileUtils
+import kotlinx.serialization.SerializationException
 import java.io.File
 import java.io.IOException
 import java.math.BigInteger
@@ -75,6 +76,7 @@ fun loadCustomLayout(layoutContent: String, layoutName: String, languageTag: Str
         .show()
 }
 
+/** @return true if json, false if simple, null if invalid */
 private fun checkLayout(layoutContent: String, context: Context): Boolean? {
     val params = KeyboardParams()
     params.mId = KeyboardLayoutSet.getFakeKeyboardId(KeyboardId.ELEMENT_ALPHABET)
@@ -85,18 +87,23 @@ private fun checkLayout(layoutContent: String, context: Context): Boolean? {
         if (!checkKeys(keys))
             return null
         return true
-    } catch (e: Exception) { Log.w(TAG, "error parsing custom json layout", e) }
+    } catch (e: SerializationException) {
+        Log.w(TAG, "json parsing error", e)
+    } catch (e: Exception) {
+        Log.w(TAG, "json layout parsed, but considered invalid", e)
+        return null
+    }
     try {
         val keys = RawKeyboardParser.parseSimpleString(layoutContent).map { row -> row.map { it.toKeyParams(params) } }
         if (!checkKeys(keys))
             return null
         return false
     } catch (e: Exception) { Log.w(TAG, "error parsing custom simple layout", e) }
-    if (layoutContent.trimStart().startsWith("[")) {
+    if (layoutContent.trimStart().startsWith("[") && layoutContent.trimEnd().endsWith("]")) {
         // layout can't be loaded, assume it's json -> load json layout again because the error message shown to the user is from the most recent error
         try {
             RawKeyboardParser.parseJsonString(layoutContent).map { row -> row.mapNotNull { it.compute(params)?.toKeyParams(params) } }
-        } catch (e: Exception) { Log.w(TAG, "error parsing custom json layout", e) }
+        } catch (e: Exception) { Log.w(TAG, "json parsing error", e) }
     }
     return null
 }
diff --git a/layouts.md b/layouts.md
index e6576eb4..bad08561 100644
--- a/layouts.md
+++ b/layouts.md
@@ -58,7 +58,7 @@ If the layout has exactly 2 keys in the bottom row, these keys will replace comm
 * `codePoints`: when multiple code points should be entered, only available for `multi_text_key`
 * `label`: text to display on the key, determined from code if empty
   * There are some special values, see the [label section](#labels)
-* `groupId`: which additional popup keys to show, `0` is default and does not add anything, `1` adds the comma popup keys, and `2` adds the period popup keys
+* `groupId`: which additional popup keys to show, `0` is default and does not add anything, `1` adds the comma popup keys, `2` adds the period popup keys, `3` adds the action key popup keys (looks awkward though)
 * `popup`: list of keys to add in the popup, e.g. `"label": ")", "popup": {"relevant": [{  "label": "." }]}` is a `)` key with a `.` popup
   * Note that in popup keys, properties are ignored with the exception of `$`, `code`, `codePoints`, and `label`
   * When specifying a _selector_ key class in a popup key, it will be evaluated correctly (e.g. for changing popups dependent on shift state)