diff --git a/src/dmd/access.d b/src/dmd/access.d
index baab89c411fc..d58e5d1bd7f7 100644
--- a/src/dmd/access.d
+++ b/src/dmd/access.d
@@ -512,6 +512,20 @@ extern (C++) bool symbolIsVisible(Dsymbol origin, Dsymbol s)
 extern (C++) bool symbolIsVisible(Scope *sc, Dsymbol s)
 {
     s = mostVisibleOverload(s);
+    return checkSymbolAccess(sc, s);
+}
+
+/**
+ * Check if a symbol is visible from a given scope without taking
+ * into account the most visible overload.
+ *
+ * Params:
+ *  sc = lookup scope
+ *  s = symbol to check for visibility
+ * Returns: true if s is visible by origin
+ */
+extern (C++) bool checkSymbolAccess(Scope *sc, Dsymbol s)
+{
     final switch (s.prot().kind)
     {
     case Prot.Kind.undefined: return true;
diff --git a/src/dmd/dtemplate.d b/src/dmd/dtemplate.d
index a4dbdc27554c..d4659ce25ca0 100644
--- a/src/dmd/dtemplate.d
+++ b/src/dmd/dtemplate.d
@@ -2766,7 +2766,7 @@ void functionResolve(Match* m, Dsymbol dstart, Loc loc, Scope* sc, Objects* tiar
         if (auto td = s.isTemplateDeclaration())
             return applyTemplate(td);
         return 0;
-    });
+    }, sc);
 
     //printf("td_best = %p, m.lastf = %p\n", td_best, m.lastf);
     if (td_best && ti_best && m.count == 1)
diff --git a/src/dmd/func.d b/src/dmd/func.d
index a99637fb2fd2..6b2cc5dbc01d 100644
--- a/src/dmd/func.d
+++ b/src/dmd/func.d
@@ -2326,11 +2326,17 @@ extern (C++) Expression addInvariant(Loc loc, Scope* sc, AggregateDeclaration ad
 /***************************************************
  * Visit each overloaded function/template in turn, and call dg(s) on it.
  * Exit when no more, or dg(s) returns nonzero.
+ *
+ * Params:
+ *  fstart = symbol to start from
+ *  dg = the delegate to be called on the overload
+ *  sc = the initial scope from the calling context
+ *
  * Returns:
  *      ==0     continue
  *      !=0     done
  */
-extern (D) int overloadApply(Dsymbol fstart, scope int delegate(Dsymbol) dg)
+extern (D) int overloadApply(Dsymbol fstart, scope int delegate(Dsymbol) dg, Scope* sc = null)
 {
     Dsymbol next;
     for (Dsymbol d = fstart; d; d = next)
@@ -2339,7 +2345,22 @@ extern (D) int overloadApply(Dsymbol fstart, scope int delegate(Dsymbol) dg)
         {
             if (od.hasOverloads)
             {
-                if (int r = overloadApply(od.aliassym, dg))
+                /* The scope is needed here to check whether a function in
+                   an overload set was added by means of a private alias (or a
+                   selective import). If the scope where the alias is created
+                   is imported somewhere, the overload set is visible, but the private
+                   alias is not.
+                 */
+                if (sc)
+                {
+                    import dmd.access : checkSymbolAccess;
+                    if (checkSymbolAccess(sc, od))
+                    {
+                        if (int r = overloadApply(od.aliassym, dg, sc))
+                            return r;
+                    }
+                }
+                else if (int r = overloadApply(od.aliassym, dg, sc))
                     return r;
             }
             else
@@ -2353,7 +2374,7 @@ extern (D) int overloadApply(Dsymbol fstart, scope int delegate(Dsymbol) dg)
         {
             if (fa.hasOverloads)
             {
-                if (int r = overloadApply(fa.funcalias, dg))
+                if (int r = overloadApply(fa.funcalias, dg, sc))
                     return r;
             }
             else if (auto fd = fa.toAliasFunc())
@@ -2370,7 +2391,14 @@ extern (D) int overloadApply(Dsymbol fstart, scope int delegate(Dsymbol) dg)
         }
         else if (auto ad = d.isAliasDeclaration())
         {
-            next = ad.toAlias();
+            if (sc)
+            {
+                import dmd.access : checkSymbolAccess;
+                if (checkSymbolAccess(sc, ad))
+                    next = ad.toAlias();
+            }
+            else
+               next = ad.toAlias();
             if (next == ad)
                 break;
             if (next == fstart)
@@ -2631,7 +2659,7 @@ extern (C++) FuncDeclaration resolveFuncCall(Loc loc, Scope* sc, Dsymbol s,
                 if (num > 0)
                     .errorSupplemental(loc, "... (%d more, -v to show) ...", num);
                 return 1;   // stop iterating
-            });
+            }, sc);
         }
     }
     else if (m.nextf)
diff --git a/test/fail_compilation/fail18243.d b/test/fail_compilation/fail18243.d
new file mode 100644
index 000000000000..217910a107bb
--- /dev/null
+++ b/test/fail_compilation/fail18243.d
@@ -0,0 +1,15 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fail18243.d(14): Error: none of the overloads of `isNaN` are callable using argument types `!()(float)`
+---
+*/
+
+module fail18243;
+
+import imports.a18243;
+
+void main()
+{
+    bool b = isNaN(float.nan);
+}
diff --git a/test/fail_compilation/imports/a18243.d b/test/fail_compilation/imports/a18243.d
new file mode 100644
index 000000000000..73df7511cebc
--- /dev/null
+++ b/test/fail_compilation/imports/a18243.d
@@ -0,0 +1,5 @@
+module a18243;
+
+import std.math : isNaN;
+
+public bool isNaN() { return false; }