diff --git a/parse.c b/parse.c
index f4f57aa..6d6c65d 100644
--- a/parse.c
+++ b/parse.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
+#include <float.h>
 #include <ctype.h>
 
 #include "parse.h"                     /* my own definitions */
@@ -318,6 +319,38 @@ int get_mode(
     return TRUE;
 }
 
+/*
+ * We need 56 bits of mantissa.
+ *
+ * Try to detect if it is needed, possible and useful to use
+ * long double instead of double, when parsing floating point numbers.
+ */
+
+#if DBL_MANT_DIG >= 56
+/* plain double seems big enough */
+# define USE_LONG_DOUBLE        0
+/* long double exists and seems big enough */
+#elif LDBL_MANT_DIG >= 56
+# define USE_LONG_DOUBLE        1
+#elif defined(LDBL_MANT_DIG)
+/* long double exists but is probably still too small */
+# define USE_LONG_DOUBLE        1
+#else
+/* long double does not exist and plain double is too small */
+# define USE_LONG_DOUBLE        0
+#endif
+
+#if USE_LONG_DOUBLE
+# define DOUBLE                 long double
+# define SCANF_FMT              "%Lf"
+# define FREXP                  frexpl
+#else
+# define DOUBLE                 double
+# define SCANF_FMT              "%lf"
+# define FREXP                  frexp
+#endif
+
+
 /* Parse PDP-11 64-bit floating point format. */
 /* Give a pointer to "size" words to receive the result. */
 /* Note: there are probably degenerate cases that store incorrect
@@ -334,8 +367,8 @@ int parse_float(
     int size,
     unsigned *flt)
 {
-    double          d;          /* value */
-    double          frac;       /* fractional value */
+    DOUBLE          d;          /* value */
+    DOUBLE          frac;       /* fractional value */
     ulong64         ufrac;      /* fraction converted to 49 bit
                                    unsigned integer */
     int             i;          /* Number of fields converted by sscanf */
@@ -344,7 +377,7 @@ int parse_float(
     unsigned        uexp;       /* Unsigned excess-128 exponent */
     unsigned        sign = 0;   /* Sign mask */
 
-    i = sscanf(cp, "%lf%n", &d, &n);
+    i = sscanf(cp, SCANF_FMT "%n", &d, &n);
     if (i == 0)
         return 0;                      /* Wasn't able to convert */
 
@@ -359,7 +392,7 @@ int parse_float(
         return 1;                      /* Good job. */
     }
 
-    frac = frexp(d, &sexp);            /* Separate into exponent and mantissa */
+    frac = FREXP(d, &sexp);            /* Separate into exponent and mantissa */
     if (sexp < -127 || sexp > 127)
         return 0;                      /* Exponent out of range. */
 
diff --git a/tests/test-float.lst.ok b/tests/test-float.lst.ok
new file mode 100644
index 0000000..620b658
--- /dev/null
+++ b/tests/test-float.lst.ok
@@ -0,0 +1,50 @@
+       1                                ;;;;;
+       2                                ;
+       3                                ; Test floating point numbers
+       4                                
+       5 000000 040200                          .word   ^F 1.0          ; 040200
+       6 000002 140200                          .word   ^F-1.0          ; 140200
+       7 000004 137600                          .word   -^F 1.0         ; 137600
+       8 000006 037600                          .word   -^F-1.0         ; 037600
+       9                                
+      10 000010 040706                          .word   ^F6.2           ; 040706
+      11 000012 137071                          .word   ^C^F6.2         ; 137071
+      12 000014 137071                          .word   ^C<^F6.2>       ; 137071
+      13                                
+      14 000016 040706  063146                  .flt2   6.2             ; 040706 063146
+      15 000022 040706  063146  063146          .flt4   6.2             ; 040706 063146 063146 063146
+         000030 063146                  
+      16                                
+      17 000032 040300  000000                  .flt2   1.5             ; 040300 000000
+      18 000036 040300  000000  000000          .flt4   1.5             ; 040300 000000 000000 000000
+         000044 000000                  
+      19                                
+      20 000046 056200                          .word   ^F 72057594037927935  ; 056200 (rounded!)
+      21 000050 056200  000000                  .flt2   72057594037927935     ; 056200 000000 (rounded!)
+      22 000054 056177  177777  177777          .flt4   72057594037927935     ; 056177 177777 177777 177777 (exact!)
+         000062 177777                  
+      23                                
+      24 000064 056200                          .word   ^F 72057594037927936  ; 056200
+      25 000066 056200  000000                  .flt2   72057594037927936     ; 056200 000000
+      26 000072 056200  000000  000000          .flt4   72057594037927936     ; 056200 000000 000000 000000
+         000100 000000                  
+      27                                
+      28 000102 056200  000000  000000          .flt4   72057594037927937     ; 056200 000000 000000 000001
+         000110 000000                  
+      29                                
+      30 000112 056400  000000  000000          .flt4   144115188075855873    ; 1 << 57 +1
+         000120 000000                  
+      31                                                                      ; 056400 000000 000000 000000 (rounded!)
+      32                                
+      32                                
+
+
+Symbol table
+
+.      ******R      001 
+
+
+Program sections:
+
+. ABS.  000000    000   (RW,I,GBL,ABS,OVR,NOSAV)
+        000122    001   (RW,I,LCL,REL,CON,NOSAV)
diff --git a/tests/test-float.mac b/tests/test-float.mac
index 3459c0c..3159c9f 100644
--- a/tests/test-float.mac
+++ b/tests/test-float.mac
@@ -26,3 +26,7 @@
         .flt4   72057594037927936     ; 056200 000000 000000 000000
 
         .flt4   72057594037927937     ; 056200 000000 000000 000001
+
+        .flt4   144115188075855873    ; 1 << 57 +1
+                                      ; 056400 000000 000000 000000 (rounded!)
+