diff --git a/CHANGELOG.md b/CHANGELOG.md
index fdd9803e..1d74c846 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 0.27 - TBD
+
+Bug Fixes
+
+- Prevent the compiler from inlining calls to primitives that open ports, avoiding a range of issues such as an open file operation being inlined across multiple places in the intermediate code.
+
 ## 0.26 - February 3, 2021
 
 Features
diff --git a/scheme/cyclone/cps-optimizations.sld b/scheme/cyclone/cps-optimizations.sld
index 56ef7f75..890dcd17 100644
--- a/scheme/cyclone/cps-optimizations.sld
+++ b/scheme/cyclone/cps-optimizations.sld
@@ -156,13 +156,18 @@
         global 
         defined-by 
         defines-lambda-id
-        const const-value  
-        ref-count ref-by
+        const 
+        const-value  
+        ref-count 
+        ref-by
         mutated-by-set
-        reassigned assigned-value 
-        app-fnc-count app-arg-count
+        reassigned 
+        assigned-value 
+        app-fnc-count 
+        app-arg-count
         cannot-inline
-        inlinable mutated-indirectly
+        inlinable 
+        mutated-indirectly
         cont
         def-in-loop
         ref-in-loop
@@ -1173,6 +1178,10 @@
           Cyc-fast-vector-3
           Cyc-fast-vector-4
           Cyc-fast-vector-5
+          open-input-file
+          open-output-file
+          open-binary-input-file
+          open-binary-output-file
           )))
 
     (define (prim-calls-inlinable? prim-calls)