diff --git a/README.md b/README.md
index 939408f..7539ab9 100644
--- a/README.md
+++ b/README.md
@@ -87,7 +87,7 @@ RUN install-php-extensions gd xdebug
| odbc | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| opcache | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| opencensus | | | ✓ | ✓ | ✓ | ✓ | ✓ |
-| parallel | | | | ✓ | ✓ | ✓ | ✓ |
+| parallel[*](#special-requirements-for-parallel) | | | | ✓ | ✓ | ✓ | ✓ |
| pcntl | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| pcov | | | ✓ | ✓ | ✓ | ✓ | ✓ |
| pdo_dblib | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
@@ -100,7 +100,7 @@ RUN install-php-extensions gd xdebug
| propro | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| protobuf | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| pspell | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
-| pthreads | ✓ | ✓ | ✓ | | | | |
+| pthreads[*](#special-requirements-for-pthreads) | ✓ | ✓ | ✓ | | | | |
| raphf | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| rdkafka | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| recode | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | |
@@ -117,7 +117,7 @@ RUN install-php-extensions gd xdebug
| sysvmsg | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| sysvsem | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| sysvshm | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
-| tdlib | | | ✓ | ✓ | ✓ | ✓ | ✓ |
+| tdlib[*](#special-requirements-for-tdlib) | | | ✓ | ✓ | ✓ | ✓ | ✓ |
| tidy | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| timezonedb | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| uopz | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
@@ -189,9 +189,9 @@ Some extension has special requirements:
| Extension | Requirements |
|---|---|
-| parallel | Requires images with PHP compiled with thread-safety enabled (`zts`). |
-| pthreads | Requires images with PHP compiled with thread-safety enabled (`zts`). |
-| tdlib | • Not available in `alpine3.7` docker images
• Not available in `jessie` docker images |
+| parallel | Requires images with PHP compiled with thread-safety enabled (`zts`). |
+| pthreads | Requires images with PHP compiled with thread-safety enabled (`zts`). |
+| tdlib | • Not available in `alpine3.7` docker images
• Not available in `jessie` docker images |