diff --git a/esp-wifi/src/wifi/mod.rs b/esp-wifi/src/wifi/mod.rs
index 6f43d3dc..d859ee3a 100644
--- a/esp-wifi/src/wifi/mod.rs
+++ b/esp-wifi/src/wifi/mod.rs
@@ -969,7 +969,7 @@ impl Device for WifiDevice<'_> {
     ) -> Option<(Self::RxToken<'_>, Self::TxToken<'_>)> {
         critical_section::with(|cs| {
             let rx = DATA_QUEUE_RX.borrow_ref_mut(cs);
-            if !rx.is_empty() && esp_wifi_can_send() {
+            if !rx.is_empty() && esp_wifi_can_send(cs) {
                 Some((WifiRxToken::default(), WifiTxToken::default()))
             } else {
                 None
@@ -978,12 +978,13 @@ impl Device for WifiDevice<'_> {
     }
 
     fn transmit(&mut self, _instant: smoltcp::time::Instant) -> Option<Self::TxToken<'_>> {
-        if esp_wifi_can_send() {
-            Some(WifiTxToken::default())
-        } else {
-            warn!("no Tx token available");
-            None
-        }
+        critical_section::with(|cs| {
+            if esp_wifi_can_send(cs) {
+                Some(WifiTxToken::default())
+            } else {
+                None
+            }
+        })
     }
 
     fn capabilities(&self) -> smoltcp::phy::DeviceCapabilities {
@@ -1061,8 +1062,9 @@ where
     res
 }
 
-fn esp_wifi_can_send() -> bool {
+fn esp_wifi_can_send(cs: critical_section::CriticalSection) -> bool {
     WIFI_TX_INFLIGHT.load(Ordering::SeqCst) < TX_QUEUE_SIZE
+        && crate::HEAP.borrow_ref(cs).free() > 2 * DATA_FRAME_SIZE
 }
 
 // FIXME data here has to be &mut because of `esp_wifi_internal_tx` signature, requiring a *mut ptr to the buffer
@@ -1310,7 +1312,7 @@ pub(crate) mod embassy {
 
             critical_section::with(|cs| {
                 let rx = DATA_QUEUE_RX.borrow_ref_mut(cs);
-                if !rx.is_empty() && esp_wifi_can_send() {
+                if !rx.is_empty() && esp_wifi_can_send(cs) {
                     Some((WifiRxToken::default(), WifiTxToken::default()))
                 } else {
                     None
@@ -1320,11 +1322,14 @@ pub(crate) mod embassy {
 
         fn transmit(&mut self, cx: &mut core::task::Context) -> Option<Self::TxToken<'_>> {
             TRANSMIT_WAKER.register(cx.waker());
-            if esp_wifi_can_send() {
-                Some(WifiTxToken::default())
-            } else {
-                None
-            }
+
+            critical_section::with(|cs| {
+                if esp_wifi_can_send(cs) {
+                    Some(WifiTxToken::default())
+                } else {
+                    None
+                }
+            })
         }
 
         fn link_state(&mut self, cx: &mut core::task::Context) -> embassy_net_driver::LinkState {